16
16
if (length(levels(as.factor(cc)))<2) stop("cc status is monomorphic!")
18
18
if (levels(as.factor(cc))[1] != 0 || levels(as.factor(cc))[2] != 1) stop ("cc is case-control status, with 0 as control and 1 as cases. No 0 and/or 1 found in the data")