[R] randomForests predict problem

[Liaw, Andy]

Yves,

Which version of the package are you using?  I get:

> soy <- na.omit(Soybean)
> ts <- sample(nrow(soy), 150, replace=FALSE)
> sb.rf <- randomForest(Class ~ ., data=soy[-ts,])
> table(predict(sb.rf, soy[ts,], type="class"))

               2-4-d-injury         alternarialeaf-spot 
                          0                          37 
                anthracnose            bacterial-blight 
                         10                           3 
          bacterial-pustule                  brown-spot 
                          2                          29 
             brown-stem-rot                charcoal-rot 
                         11                           7 
              cyst-nematode diaporthe-pod-&-stem-blight 
                          0                           0 
      diaporthe-stem-canker                downy-mildew 
                          4                           8 
         frog-eye-leaf-spot            herbicide-injury 
                         17                           0 
     phyllosticta-leaf-spot            phytophthora-rot 
                          3                           5 
             powdery-mildew           purple-seed-stain 
                          4                           5 
       rhizoctonia-root-rot 
                          5 

Cheers,
Andy

> -----Original Message-----
> From: Yves Brostaux [mailto:brostaux.y at fsagx.ac.be]
> Sent: Wednesday, April 02, 2003 4:46 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] randomForests predict problem
> 
> 
> Hello everybody,
> 
> I'm testing the randomForest package in order to do some 
> simulations and I 
> get some trouble with the prediction of new values. The random forest 
> computation is fine but each time I try to predict values 
> with the newly 
> created object, I get an error message. I thought I was 
> because NA values 
> in the dataframe, but I cleaned them and still got the same 
> error. What am 
> I doing wrong ?
> 
>  > library(mlbench)
>  > library(randomForest)
>  > data(Soybean)
>  > test <- sample(1:683, 150, replace=F)
>  > sb.rf <- randomForest(Class~., data=Soybean[-test,])
>  > sb.rf.pred <- predict(sb.rf, Soybean[test,])
> Error in matrix(t1$countts, nr = nclass, nc = ntest) :
>          No data to replace in matrix(...)
> 
> I did it the same way with rpart and all worked fine :
>  > library(rpart)
>  > sb.rp <- rpart(Class~., data=Soybean[-test,])
>  > sb.rp.pred <- predict(sb.rp, Soybean[test,], type="class")
> 
> Thank you all for any advice you can give to me.
> 
> -- 
> Ir. Yves Brostaux - Statistics and Computer Science Dpt.
> Gembloux Agricultural University
> 8, avenue de la Faculté B-5030 Gembloux (Belgium)
> Tél : +32 (0)81 62 24 69
> E-mail : brostaux.y at fsagx.ac.be
> Web : http://www.fsagx.ac.be/si/
> 
> ______________________________________________
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