ipd1: a dataframe with n1 row and p column, where n1 is number of subjects of the first IPD, and p is the number of variables used in standardization.
ipd2: a dataframe with n2 row and p column, where n2 is number of subjects of the second IPD, and p is the number of variables used in standardization.
vars_to_match: variables used for matching. if NULL, use all variables.
cat_vars_to_01: variable names for the categorical variables that need to be converted to indicator variables.
mean.constrained: whether to restrict the weighted means to be within the ranges of observed means. Default is FALSE. When it is TRUE, there is a higher chance of not having a solution.
Returns
lp.check: 0 = OS can be conducted; 2 = OS cannot be conducted
Details
If dummy variables are already created for the categorical variables in the data set, and are present in ipd1 and ipd2, then cat_vars_to_01 should be left as NULL.