当我们想将 R 中的随机森林函数应用于超过 53 个类别的预测器时，解决方案是什么？

> RandomForestPrediction=function(alpha){
+   d = sort(sample(nrow(MPS), nrow(MPS)*alpha))
+   train<-MPS[d,]
+   test<-MPS[-d,]
+   myNtree=1000
+   myMtry=5
+   myImportance=TRUE
+   mod2 = randomForest(factor(m.Decision)~.,data=train,tree=myNtree,mtry=myMtry,importance=myImportance)
+   fitted=predict(mod2,test,type="response")
+   return(table(fitted,test$m.Decision))
+ }
> RandomForestPrediction(0.7)
Error in randomForest.default(m, y, ...) : 
Can not handle categorical predictors with more than 53 categories.