Hmm, I'm not sure how to reproduce your error.
svmRadial is a method in caret, not a function, so I'm not sure why you'd be getting that error (example from SO thread, below):
library(caret)
#> Loading required package: lattice
#> Loading required package: ggplot2
data(iris)
TrainData <- iris[,1:4]
TrainClasses <- iris[,5]
out1 <- train(TrainData, TrainClasses, method = "svmRadial")
class(out1$finalModel)
#> [1] "ksvm"
#> attr(,"package")
#> [1] "kernlab"
Created on 2018-07-10 by the reprex package (v0.2.0).
Could you please turn this into a self-contained reprex (short for reproducible example)? It will help us help you if we can be sure we're all working with/looking at the same stuff.
install.reprex("reprex")
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