RF+BK: compute sum of weighted correlations in cosmo_correlation_measure, rather than the mean. This should not affect group statistics (because it scales the data) but can affect results from individual subjects
RF: update test to reflect change in correlation_measure
RF: use ds as most common input
EXC: update classification exercise
EXC+SML: add link to naive bayes classifier
EXC: update cross validation exercise
EXC+SML: add header ref
RF+EXC: clarify split-half correlation exercises
SML: clarify removing constant features
DOC: split exercise in two parts
EXC: add use of cosmo_nfold_partiioners
EXC+SML+RF: preallocate space for output
EXC+RF: explain rationale of correlation difference
NF: figure showing nfold_crossvalidation_classification
NF: figure showing splithalf_correlation