I’m doing a Random Forest analysis (perturb = list(replace = TRUE), ntree = 1500, mtry = 3) with the cforest function from the library partykit with a large number of predictor variables (altogether 13) and want to determine conditional variable importances using the varimp function. However, I get this error (no error, if conditional = FALSE!):

Error in FUN(model = model, trafo = trafo, data = data, subset = subset,  : 
  NROW(Y) == length(ix) is not TRUE

Does anyone know the error and know how to get rid of it?