statsmodels/statsmodels — comment on commit 312ca86916740ac83cbac277941db71376348778
File: scikits/statsmodels/sandbox/tools/tools_pca.py line 102
By josef-pkt:

demean is redundant if only cov or corr are possible (they always demean)

the third case should be raw moment x'x, i.e. cov with assumption mean=0