[R] indexing by empty string (was RE: Error in predict.randomForest ... subscript out of bounds with NULL name in X)

[Liaw, Andy]

I'm not exactly sure if this is a problem with indexing by name; i.e., is the following behavior by design?  The problem is that names or dimnames that are empty seem to be treated differently, and one can't index by them:

R> junk = 1:3
R> names(junk) = c("a", "b", "")
R> junk
a b   
1 2 3 
R> junk[""]
<NA> 
  NA 
R> junk = matrix(1:4, 2, 2)
R> colnames(junk) = c("a", "")
R> junk[, ""]
Error: subscript out of bounds

I may need to find workaround...

 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Czerminski, Ryszard
> Sent: Wednesday, January 25, 2012 10:39 AM
> To: r-help at r-project.org
> Subject: [R] Error in predict.randomForest ... subscript out 
> of bounds with NULL name in X
> 
> RF trains fine with X, but fails on prediction
> 
> > library(randomForest)
> > chirps <-
> c(20,16.0,19.8,18.4,17.1,15.5,14.7,17.1,15.4,16.2,15,17.2,16,17,14.1)
> > temp <-
> c(88.6,71.6,93.3,84.3,80.6,75.2,69.7,82,69.4,83.3,78.6,82.6,80
> .6,83.5,76
> .3)
> > X <- cbind(1,chirps)
> > rf <- randomForest(X, temp)
> > yp <- predict(rf, X)
> Error in predict.randomForest(rf, X) : subscript out of bounds
> 
> BTW: Just find out that  apparently predict() does not like 
> NULL name in
> X, because this works fine:
> 
> > one <- rep(1, length(chirps))
> > X <- cbind(one,chirps)
> > rf <- randomForest(X, temp)
> > yp <- predict(rf, X)
> 
> Ryszard Czerminski
> AstraZeneca Pharmaceuticals LP
> 35 Gatehouse Drive
> Waltham, MA 02451
> USA
> 781-839-4304
> ryszard.czerminski at astrazeneca.com
> 
> 
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