Dear list I'm classifying some data with e1071package but when I try to tune my parameters I retrieve this error Error in do.call(method, c(list(train.x[train.ind[[sample]], ], y train.y[train.ind[[sample]]]), : 'what' must be a character string or a function below are my command training<-read.csv(file="tabtraining",header=T,row.names=c(1),sep="\t",na.strings="NA") datatraining=subset(training,select=-Response) classtraining<-Stato classtraining<-subset(training,select=Reponse) test<-read.csv(file="tabtest",header=T,row.names=c(1),sep="\t",na.strings="NA") datatest=subset(test,select=-Stato) classtest<-subset(test,select=Stato) model<-svm(datatraining,classtraining,type="C-classification") tune(model,train.x=datatraining,train.y=classtraining,validation.x=datatest,validation.y=classtest, ranges = list(gamma = 2^(-1:1), cost = 2^(2:4)), control tune.control(sampling = "fix")) any tips are welcome ;-) Thank you very much Guido [[alternative HTML version deleted]]