I am trying to set up a mixture model using flex mix. I have a response vector Y, a set of predictors X and grouping variables Z. When i try to run flexmix i get the error below.Am i coding it wrong? fit1 <- flexmix(formula=Y~X|Z, data = data, k=3, cluster = NULL, model=NULL, concomitant=NULL, control=list(class="Z"), weights=NULL) Error in function (classes, fdef, mtable) : unable to find an inherited method for function "flexmix", for signature "formula", "data.frame", "numeric", "NULL", "NULL" Thanks. [[alternative HTML version deleted]]