Package: omoment
OMoment: Efficient online calculation of statistical momentsOMoment package calculates moments of statistical distributions (means, variances, covariance) in online or
distributed settings for univariate and bivariate distributions.Suitable for large data – works well with numpy and Pandas and in distributed setting.Moments calculated from different parts of data can be easily combined or updated for new data (supports addition
of results).Objects are lightweight, calculation is done in numpy if possible.Weights for data can be provided.Invalid values (NaNs, infinities are omitted by default).Typical application is calculation of means and variances (or even correlation of two variables) of many chunks of data
(corresponding to different groups or to different parts of the distributed data), the results can be analyzed on level
of the groups or easily combined to get exact moments for the full dataset.Basic examplefromomomentimportOMeanVarimportnumpyasnpimportpandasaspdrng=np.random.default_rng(12354)g=rng.integers(low=0,high=10,size=1000)x=g+rng.normal(loc=0,scale=10,size=1000)w=rng.exponential(scale=1,size=1000)# calculate overall momentsOMeanVar.compute(x,w)# should give: OMeanVar(mean=4.6, var=108, weight=1.08e+03)# or calculate moments for every groupdf=pd.DataFrame({'g':g,'x':x,'w':w})omvs=df.groupby('g').apply(OMeanVar.of_frame,x='x',w='w')# and combine group moments to obtain the same overall resultsOMeanVar.combine(omvs)# addition is also supportedomvs.loc[0]+omvs.loc[1]At the moment, univariate and bivariate distributions are supported. Bivariate distributions allow for fast linear
regression with two variables (and constant) calculation. Even multivariate distributions can be
efficiently processed in a similar fashion, so the support for them might be added in the future. Moments of
multivariate distributions would also allow for linear regression estimation and other statistical methods
(such as PCA or regularized regression) to be calculated in a single pass through large distributed datasets.Similar packagesOMoment package aims for fast calculation of weighted distribution moments (mean and variance at the moment),
great compatibility with numpy and pandas and suitability for distributed datasets (composability of results).
I have not found a package that would satisfy this, even though similar packages indeed exist.RunStatsRunStatspackage calculates several moments of univariate distribution (including skewness and kurtosis)
and a few other statistics (min and max) and the results can be combined together. In addition, it provides Regression
object for bivariate statistics. It does not support weights and the calculation was more than 100x slower in my
testing (admittedly I am not sure if I used cython support correctly).importnumpyasnpfromomomentimportOMeanVarfromrunstatsimportStatisticsimporttimerng=np.random.Generator(np.random.PCG64(12345))x=rng.normal(size=1_000_000)start=time.time()omv=OMeanVar.compute(x)end=time.time()print(f'{end-start:.3g}seconds')# 0.0146 secondsstart=time.time()st=Statistics(x)end=time.time()print(f'{end-start:.3g}seconds')# 2.83 secondsGymOpenAI Gym(or newlyGymnasium)
provides similar functionality as a part of its normalization of observations and rewards
(in gym.wrappers.normalize.RunningMeanStd). The functionality is fairly limited as it was developed for a particular
use case, but the calculation is fast, and it is possible to compose the results. It does not support weights though.Documentationhttps://protivinsky.github.io/omoment/index.html