CHAID with r-caret error x is not a factor - r

Question

I am using the CHAID method from caret. I am getting the same error as this post that x is not a factor when all the x's are factors.
I'm using R 3.3.3 and caret_6.0-78
Here is a toy example:
library(datasets)
library(caret)
library(CHAID)
testDat<-data.frame(HairEyeColor, stringsAsFactors=T)[,1:3]
str(testDat)
'data.frame': 32 obs. of 3 variables:
$ Hair: Factor w/ 4 levels "Black","Brown",..: 1 2 3 4 1 2 3 4 1 2 ...
$ Eye : Factor w/ 4 levels "Brown","Blue",..: 1 1 1 1 2 2 2 2 3 3 ...
$ Sex : Factor w/ 2 levels "Male","Female": 1 1 1 1 1 1 1 1 1 1 ...
control <- trainControl(method="repeatedcv", number=10, repeats=3,
+ savePredictions="final", summaryFunction=twoClassSummary, classProbs=TRUE)
fit.chaid <- train(Sex~Hair+Eye, data=testDat, method="chaid", metric="ROC", trControl=control)
Error: is.factor(x) is not TRUE
In addition: There were 50 or more warnings (use warnings() to see the first 50)
Timing stopped at: 0.02 0 0.02
warnings()
Warning messages:
1: model fit failed for Fold01.Rep1: alpha2=0.05, alpha3=-1, alpha4=0.05 Error : is.factor(x) is not TRUE
.
.

Answer 1

I know that this question already old, but here I got the answers for it by experimenting:
For CHAID Modeling, try to use xy modeling rather than formula modeling, like this:
fit.chaid <- train(x=testDat[,c(1,2)], #Hair and Eye Variable
y=testDat[,c(3)], #Sex Variable
method="chaid",
metric="ROC",
trControl=control)