twoStepTransform
is a transformation that can
be applied to a matrix of data. The resulting matrix is both
subject-centered and bias corrected, a technique called
the CM technique b12,c05,m08superb
twoStepTransform(dta, variables)
a data.frame of the same form as dta with the variables transformed.
This function is useful when passed to the argument preprocessfct
of superbPlot()
where it performs a modification of the data matrix.
a data.frame containing the data in wide format;
a vector of column names on which the transformation will be applied. the remaining columns will be left unchanged