Given a dataframe, scale and center the continous features
scale_center(x, categoricalFeatureCols, colMeans, colSd)A dataframe in order to be processed.
A vector of the categorical features, we don't want to scale/center these. Should be 1-indexed.
A vector of the means to center each column.
A vector of the standard deviations to scale each column with.
A scaled and centered dataset x