Patent ID: 8140456

Claim:
A method of extracting factors that distinguish between two groups, comprising: (a) receiving, from a sample database stored in a storage medium, a set of samples, wherein each sample comprises a set of factors having quantitative values, and wherein each sample belongs to one of two groups (X and Y); (b) creating, using a CPU, a first virtual sample set (X t ) by randomly sampling the set of samples belonging to the first group; (c) creating, using the CPU, a second virtual sample set (Y t ) by randomly sampling the set of samples belonging to the second group; (d) calculating the mean (μ i (X t )) and variance ( σ i 2 ⁡ ( X t ) ) of the quantitative values for each factor of the samples in the first virtual sample set; (e) calculating the mean (μ i (Y t )) and variance ( σ i 2 ⁡ ( Y t ) ) of the quantitative values for each factor of the samples in the second virtual sample set; (f) calculating, using the CPU, the Fisher ratio ( F i ⁡ ( X t , Y t ) = ( μ i ⁡ ( X t ) - μ i ⁡ ( Y t ) ) 2 P x ⁢ σ i 2 ⁡ ( X t ) + P y ⁢ σ i 2 ⁡ ( Y t ) ) of each factor, wherein P x and P y are the prior probabilities of a sample belonging to X or Y, respectively; (g) using the Fisher ratios to identify factors that are effective to distinguish the two groups; (h) combining the identified factors and their corresponding Fisher ratios (F i ) into a factor subset; (i) repeating steps (b)-(h), thereby generating a plurality of factor subsets; (j) determining the frequency of each factor in the plurality of factor subsets; (k) extracting the factors having a frequency that exceeds a chosen threshold; (l) combining the extracted factors, and a set (F i ) of the Fisher ratios corresponding to each extracted factor, into a target factor set; (m) calculating the mean (μ(F i )) and variance (σ 2 (F i )) of the set of Fisher ratios of each factor in the target factor set; (n) calculating, using the CPU, a generalized Fisher ratio ( F i * ) of each factor in the target factor set using the function F i * = H ⁡ ( μ ⁡ ( F i ) ) G ⁡ ( σ 2 ⁡ ( F i ) ) , wherein H(•) and G(•) are functions; (o) ranking the factors in the target factor set according to their generalized Fisher ratios; and (p) storing the ranked target factor set in an analysis result database in the storage medium.