Calculate standardized mean difference for each column of a matrix, given a binary treatment indicator vector.
mlr.smd(tr, X)Binary treatment indicator vector; 1 means treatment, 0 means control.
Matrix of covariates; each column is a covariate whose standardized mean difference we want to calculate. nrow(X) must be equal to length(tr).
A vector of length ncol(X), containing standardized mean differences for each column of X, given treatment variable tr.