Unexpected warning produced by safs when differences = TRUE

[gcaligari]

Hello,

Thanks for your package.

While using the package I noticed that the function safs throws an unexpected warning message about an error occurring when the default value of differences = TRUE is used.
I created a safs object using the example code from the safs help file to demonstrate this, as can be seen by the reproducible code found below.

caret version = 6.0-86
R version = 4.0.4

Thanks,
Giulia

library(caret)
#> Loading required package: lattice
#> Loading required package: ggplot2
set.seed(1)
train_data <- caret::twoClassSim(100, noiseVars = 10)
test_data  <- caret::twoClassSim(10,  noiseVars = 10)

## A short example
ctrl <- caret::safsControl(functions = rfSA,
                    method = "cv",
                    number = 3)

rf_search <- caret::safs(x = train_data[, -ncol(train_data)],
                  y = train_data$Class,
                  iters = 3,
                  safsControl = ctrl)
#> Warning in safs.default(x = train_data[, -ncol(train_data)], y =
#> train_data$Class, : An error occured when computing the variable differences

[topepo]

Thanks. I've added some additional code that gives a slightly better warning message.

The main issue was a low number of iterations. It didn't have enough permutations of the predictors to compute the differences. Doing 5+ iterations gives results and no warning.