data = read.table("test.docx") res = data[,1:10] gender = data[,"gender"] library("mirt") people = nrow(res) itemnum = ncol(res) group = rep('0_male', people) group[gender==1] = "1_female" mg = multipleGroup( res, model = 1, group = group, itemtype = "gpcm", invariance = c('slopes', 'intercepts', 'free_var','free_means'), method = "EM", dentype = "Gaussian" ) coef(mg, simplify=TRUE) library("regDIF") fit <- regDIF(item.data = res, pred.data = gender ,item.type="2pl", num.tau = 5,control=list(tol=1e-4) ,anchor=1:itemnum,tau=0) fit$impact fit$base