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import numpy as np |
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import scipy as sp |
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import scipy.stats as st |
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import itertools as it |
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def binomial_sign_test(*args): |
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""" |
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Performs a binomial sign test for two dependent samples. |
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Tests the hypothesis that the two dependent samples represent two different populations. |
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Parameters |
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---------- |
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sample1, sample2: array_like |
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The sample measurements for each group. |
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Returns |
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------- |
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B-value : float |
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The computed B-value of the test. |
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p-value : float |
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The associated p-value from the B-distribution. |
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|
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References |
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---------- |
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D.J. Sheskin, Handbook of parametric and nonparametric statistical procedures. |
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crc Press, 2003, Test 19: The Binomial Sign Test for Two Dependent Samples |
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""" |
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k = len(args) |
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if k != 2: raise ValueError('The test needs two samples') |
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n = len(args[0]) |
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d_plus = 0 |
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d_minus = 0 |
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for i in range(n): |
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if args[0][i] < args[1][i]: |
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d_plus = d_plus+1 |
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elif args[0][i] > args[1][i]: |
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d_minus = d_minus+1 |
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x = max(d_plus, d_minus) |
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n = d_plus + d_minus |
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p_value = 2*(1 - st.binom.cdf(x, n, 0.5)) |
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return x, p_value |
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def friedman_aligned_ranks_test(S): |
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""" |
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Performs a Friedman aligned ranks ranking test. |
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Tests the hypothesis that in a set of k dependent samples groups (where k >= 2) |
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at least two of the groups represent populations with different median values. |
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The difference with a friedman test is that it uses the median of each group to |
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construct the ranking, which is useful when the number of samples is low. |
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Parameters |
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---------- |
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S = [sample1, sample2, ... sample_k] : matrix(n,k) |
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The sample measurements (matrix columns) for each group. |
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Returns |
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------- |
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Chi2-value : float |
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The computed Chi2-value of the test. |
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p-value : float |
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The associated p-value from the Chi2-distribution. |
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rankings : array_like |
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The ranking for each group. |
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pivots : array_like |
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The pivotal quantities for each group. |
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References |
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---------- |
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J.L. Hodges, E.L. Lehmann, Ranks methods for combination of independent experiments |
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in analysis of variance, Annals of Mathematical Statistics 33 (1962) 482β497. |
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""" |
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n,k = S.shape |
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aligned_observations = [] |
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for i in range(n): |
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loc = sp.mean(S[i]) |
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aligned_observations.extend(S[i]-loc) |
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aligned_observations_sort = sorted(aligned_observations) |
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aligned_ranks = [] |
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for i in range(n): |
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row = [] |
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for j in range(k): |
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v = aligned_observations[i*k+j] |
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row.append(aligned_observations_sort.index(v) + 1 + (aligned_observations_sort.count(v)-1)/2.) |
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aligned_ranks.append(row) |
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rankings_avg = [sp.mean([case[j] for case in aligned_ranks]) for j in range(k)] |
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rankings_cmp = [r/sp.sqrt(k*(n*k+1)/6.) for r in rankings_avg] |
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r_i = [np.sum(case) for case in aligned_ranks] |
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r_j = [np.sum([case[j] for case in aligned_ranks]) for j in range(k)] |
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T = (k-1) * (sp.sum(v**2 for v in r_j) - (k*n**2/4.) * (k*n+1)**2) / float(((k*n*(k*n+1)*(2*k*n+1))/6.) - (1./float(k))*sp.sum(v**2 for v in r_i)) |
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p_value = 1 - st.chi2.cdf(T, k-1) |
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return T, p_value, rankings_avg, rankings_cmp |
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def quade_test(*args): |
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""" |
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Performs a Quade ranking test. |
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Tests the hypothesis that in a set of k dependent samples groups (where k >= 2) at least two of the groups represent populations with different median values. |
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The difference with a friedman test is that it uses the median for each sample to wiehgt the ranking. |
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Parameters |
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---------- |
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sample1, sample2, ... : array_like |
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The sample measurements for each group. |
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Returns |
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------- |
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F-value : float |
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The computed F-value of the test. |
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p-value : float |
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The associated p-value from the F-distribution. |
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rankings : array_like |
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The ranking for each group. |
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pivots : array_like |
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The pivotal quantities for each group. |
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References |
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---------- |
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D. Quade, Using weighted rankings in the analysis of complete blocks with additive block effects, Journal of the American Statistical Association 74 (1979) 680β683. |
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""" |
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k = len(args) |
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if k < 2: raise ValueError('Less than 2 levels') |
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n = len(args[0]) |
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if len(set([len(v) for v in args])) != 1: raise ValueError('Unequal number of samples') |
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rankings = [] |
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ranges = [] |
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for i in range(n): |
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row = [col[i] for col in args] |
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ranges.append(max(row) - min(row)) |
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row_sort = sorted(row) |
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rankings.append([row_sort.index(v) + 1 + (row_sort.count(v)-1)/2. for v in row]) |
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ranges_sort = sorted(ranges) |
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ranking_cases = [ranges_sort.index(v) + 1 + (ranges_sort.count(v)-1)/2. for v in ranges] |
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S = [] |
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W = [] |
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for i in range(n): |
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S.append([ranking_cases[i] * (r - (k + 1)/2.) for r in rankings[i]]) |
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W.append([ranking_cases[i] * r for r in rankings[i]]) |
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Sj = [np.sum(row[j] for row in S) for j in range(k)] |
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Wj = [np.sum(row[j] for row in W) for j in range(k)] |
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rankings_avg = [w / (n*(n+1)/2.) for w in Wj] |
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rankings_cmp = [r/sp.sqrt(k*(k+1)*(2*n+1)*(k-1)/(18.*n*(n+1))) for r in rankings_avg] |
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A = sp.sum(S[i][j]**2 for i in range(n) for j in range(k)) |
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B = sp.sum(s**2 for s in Sj)/float(n) |
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F = (n-1)*B/(A-B) |
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p_value = 1 - st.f.cdf(F, k-1, (k-1)*(n-1)) |
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return F, p_value, rankings_avg, rankings_cmp |
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def bonferroni_dunn_test(ranks, control=None): |
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""" |
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Performs a Bonferroni-Dunn post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of the control method is different to each of the other methods. |
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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control : string optional |
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The name of the control method (one vs all), default None (all vs all) |
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
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Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
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The associated p-value from the Z-distribution wich depends on the index of the comparison |
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Adjusted p-values : array-like |
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The associated adjusted p-values wich can be compared with a significance level |
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References |
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---------- |
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O.J. Dunn, Multiple comparisons among means, Journal of the American Statistical Association 56 (1961) 52β64. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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if not control : |
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control_i = values.index(min(values)) |
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else: |
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control_i = keys.index(control) |
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comparisons = [keys[control_i] + " vs " + keys[i] for i in range(k) if i != control_i] |
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z_values = [abs(values[control_i] - values[i]) for i in range(k) if i != control_i] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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adj_p_values = [min((k-1)*p_value,1) for p_value in p_values] |
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return comparisons, z_values, p_values, adj_p_values |
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def holm_test(ranks, control=None): |
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""" |
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Performs a Holm post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of the control method is different to each of the other methods. |
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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control : string optional |
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The name of the control method (one vs all), default None (all vs all) |
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
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Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
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The associated p-value from the Z-distribution wich depends on the index of the comparison |
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Adjusted p-values : array-like |
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The associated adjusted p-values wich can be compared with a significance level |
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References |
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---------- |
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O.J. S. Holm, A simple sequentially rejective multiple test procedure, Scandinavian |
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Journal of Statistics 6 (1979) 65β70. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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if not control : |
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control_i = values.index(min(values)) |
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else: |
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control_i = keys.index(control) |
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comparisons = [keys[control_i] + " vs " + keys[i] for i in range(k) if i != control_i] |
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z_values = [abs(values[control_i] - values[i]) for i in range(k) if i != control_i] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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adj_p_values = [min(max((k-(j+1))*p_values[j] for j in range(i+1)), 1) for i in range(k-1)] |
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return comparisons, z_values, p_values, adj_p_values |
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def hochberg_test(ranks, control=None): |
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""" |
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Performs a Hochberg post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of the control method is different to each of the other methods. |
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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control : string optional |
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The name of the control method, default the group with minimum ranking |
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
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Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
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The associated p-value from the Z-distribution wich depends on the index of the comparison |
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Adjusted p-values : array-like |
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The associated adjusted p-values wich can be compared with a significance level |
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References |
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---------- |
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Y. Hochberg, A sharper Bonferroni procedure for multiple tests of significance, |
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Biometrika 75 (1988) 800β803. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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if not control : |
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control_i = values.index(min(values)) |
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else: |
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control_i = keys.index(control) |
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comparisons = [keys[control_i] + " vs " + keys[i] for i in range(k) if i != control_i] |
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z_values = [abs(values[control_i] - values[i]) for i in range(k) if i != control_i] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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adj_p_values = [min(max((k-j)*p_values[j-1] for j in range(k-1, i, -1)), 1) for i in range(k-1)] |
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return comparisons, z_values, p_values, adj_p_values |
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def li_test(ranks, control=None): |
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""" |
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Performs a Li post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of the control method is different to each of the other methods. |
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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control : string optional |
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The name of the control method, default the group with minimum ranking |
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
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Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
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The associated p-value from the Z-distribution wich depends on the index of the comparison |
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Adjusted p-values : array-like |
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The associated adjusted p-values wich can be compared with a significance level |
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References |
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---------- |
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J. Li, A two-step rejection procedure for testing multiple hypotheses, Journal of |
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Statistical Planning and Inference 138 (2008) 1521β1527. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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if not control : |
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control_i = values.index(min(values)) |
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else: |
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control_i = keys.index(control) |
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comparisons = [keys[control_i] + " vs " + keys[i] for i in range(k) if i != control_i] |
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z_values = [abs(values[control_i] - values[i]) for i in range(k) if i != control_i] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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adj_p_values = [p_values[i]/(p_values[i]+1-p_values[-1]) for i in range(k-1)] |
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return comparisons, z_values, p_values, adj_p_values |
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def finner_test(ranks, control=None): |
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""" |
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Performs a Finner post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of the control method is different to each of the other methods. |
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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control : string optional |
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The name of the control method, default the group with minimum ranking |
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
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Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
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The associated p-value from the Z-distribution wich depends on the index of the comparison |
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Adjusted p-values : array-like |
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The associated adjusted p-values wich can be compared with a significance level |
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References |
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---------- |
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H. Finner, On a monotonicity problem in step-down multiple test procedures, Journal |
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of the American Statistical Association 88 (1993) 920β923. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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if not control : |
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control_i = values.index(min(values)) |
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else: |
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control_i = keys.index(control) |
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comparisons = [keys[control_i] + " vs " + keys[i] for i in range(k) if i != control_i] |
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z_values = [abs(values[control_i] - values[i]) for i in range(k) if i != control_i] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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adj_p_values = [min(max(1-(1-p_values[j])**((k-1)/float(j+1)) for j in range(i+1)), 1) for i in range(k-1)] |
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return comparisons, z_values, p_values, adj_p_values |
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def nemenyi_multitest(ranks): |
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""" |
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Performs a Nemenyi post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of each pair of groups are different. |
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
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Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
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The associated p-value from the Z-distribution wich depends on the index of the comparison |
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Adjusted p-values : array-like |
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The associated adjusted p-values wich can be compared with a significance level |
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|
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References |
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---------- |
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Bonferroni-Dunn: O.J. Dunn, Multiple comparisons among means, Journal of the American |
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Statistical Association 56 (1961) 52β64. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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versus = list(it.combinations(range(k), 2)) |
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comparisons = [keys[vs[0]] + " vs " + keys[vs[1]] for vs in versus] |
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z_values = [abs(values[vs[0]] - values[vs[1]]) for vs in versus] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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m = int(k*(k-1)/2.) |
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adj_p_values = [min(m*p_value,1) for p_value in p_values] |
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return comparisons, z_values, p_values, adj_p_values |
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def holm_multitest(ranks): |
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""" |
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Performs a Holm post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of each pair of groups are different. |
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|
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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|
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
|
Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
|
The associated p-value from the Z-distribution wich depends on the index of the comparison |
|
Adjusted p-values : array-like |
|
The associated adjusted p-values wich can be compared with a significance level |
|
|
|
References |
|
---------- |
|
O.J. S. Holm, A simple sequentially rejective multiple test procedure, Scandinavian Journal |
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of Statistics 6 (1979) 65β70. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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versus = list(it.combinations(range(k), 2)) |
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|
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comparisons = [keys[vs[0]] + " vs " + keys[vs[1]] for vs in versus] |
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z_values = [abs(values[vs[0]] - values[vs[1]]) for vs in versus] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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|
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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m = int(k*(k-1)/2.) |
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adj_p_values = [min(max((m-j)*p_values[j] for j in range(i+1)), 1) for i in range(m)] |
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return comparisons, z_values, p_values, adj_p_values |
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|
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def hochberg_multitest(ranks): |
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""" |
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Performs a Hochberg post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of each pair of groups are different. |
|
|
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Parameters |
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---------- |
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pivots : dictionary_like |
|
A dictionary with format 'groupname':'pivotal quantity' |
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|
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Returns |
|
---------- |
|
Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
|
Z-values : array-like |
|
The computed Z-value statistic for each comparison. |
|
p-values : array-like |
|
The associated p-value from the Z-distribution wich depends on the index of the comparison |
|
Adjusted p-values : array-like |
|
The associated adjusted p-values wich can be compared with a significance level |
|
|
|
References |
|
---------- |
|
Y. Hochberg, A sharper Bonferroni procedure for multiple tests of significance, Biometrika 75 (1988) 800β803. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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versus = list(it.combinations(range(k), 2)) |
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|
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comparisons = [keys[vs[0]] + " vs " + keys[vs[1]] for vs in versus] |
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z_values = [abs(values[vs[0]] - values[vs[1]]) for vs in versus] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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|
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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m = int(k*(k-1)/2.) |
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adj_p_values = [max((m+1-j)*p_values[j-1] for j in range(m, i, -1))for i in range(m)] |
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|
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return comparisons, z_values, p_values, adj_p_values |
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|
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def finner_multitest(ranks): |
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""" |
|
Performs a Finner post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of each pair of groups are different. |
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
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Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
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The associated p-value from the Z-distribution wich depends on the index of the comparison |
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Adjusted p-values : array-like |
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The associated adjusted p-values wich can be compared with a significance level |
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References |
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---------- |
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H. Finner, On a monotonicity problem in step-down multiple test procedures, Journal of the |
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American Statistical Association 88 (1993) 920β923. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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versus = list(it.combinations(range(k), 2)) |
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comparisons = [keys[vs[0]] + " vs " + keys[vs[1]] for vs in versus] |
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z_values = [abs(values[vs[0]] - values[vs[1]]) for vs in versus] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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m = int(k*(k-1)/2.) |
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adj_p_values = [min(max(1-(1-p_values[j])**(m/float(j+1)) for j in range(i+1)), 1) for i in range(m)] |
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return comparisons, z_values, p_values, adj_p_values |
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def _S(k): |
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""" |
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Helper function for the Shaffer test. |
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It obtains the number of independent test hypotheses when using an All vs |
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All strategy using the number of groups to be compared. |
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""" |
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if k == 0 or k == 1: |
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return {0} |
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else: |
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result = set() |
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for j in reversed(range(1, k+1)): |
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tmp = S(k - j) |
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for s in tmp: |
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result = result.union({sp.special.binom(j, 2) + s}) |
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return list(result) |
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def shaffer_multitest(ranks): |
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""" |
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Performs a Shaffer post-hoc test using the pivot quantities obtained by a ranking test. |
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Tests the hypothesis that the ranking of each pair of groups are different. |
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Parameters |
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---------- |
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pivots : dictionary_like |
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A dictionary with format 'groupname':'pivotal quantity' |
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|
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Returns |
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---------- |
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Comparions : array-like |
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Strings identifier of each comparison with format 'group_i vs group_j' |
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Z-values : array-like |
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The computed Z-value statistic for each comparison. |
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p-values : array-like |
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The associated p-value from the Z-distribution wich depends on the index of the comparison |
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Adjusted p-values : array-like |
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The associated adjusted p-values wich can be compared with a significance level |
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References |
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---------- |
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J. Li, A two-step rejection procedure for testing multiple hypotheses, Journal of Statistical |
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Planning and Inference 138 (2008) 1521β1527. |
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""" |
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k = len(ranks) |
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values = ranks.values() |
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keys = ranks.keys() |
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versus = list(it.combinations(range(k), 2)) |
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m = int(k*(k-1)/2.) |
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A = _S(int((1 + sp.sqrt(1+4*m*2))/2)) |
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t = [max([a for a in A if a <= m-i]) for i in range(m)] |
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comparisons = [keys[vs[0]] + " vs " + keys[vs[1]] for vs in versus] |
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z_values = [abs(values[vs[0]] - values[vs[1]]) for vs in versus] |
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p_values = [2*(1-st.norm.cdf(abs(z))) for z in z_values] |
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p_values, z_values, comparisons = map(list, zip(*sorted(zip(p_values, z_values, comparisons), key=lambda t: t[0]))) |
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adj_p_values = [min(max(t[j]*p_values[j] for j in range(i+1)), 1) for i in range(m)] |
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return comparisons, z_values, p_values, adj_p_values |