ariable Importance Measure in Package RandomForest

Given you do not want to touch the randomForest 
implementation itself, 
the answer is "no, there is no particular function to do it 
in package 
randomForest. More particular:

?randomForest tells us that a value "importance" is returned 
that is `a 
matrix with nclass + 2 (for classification) or two (for regression) 
columns. For classification, the first nclass columns are the 
class-specific measures computed as mean descrease in accuracy. The 
nclass + 1st column is the mean descrease in accuracy over 
all classes. 
The last column is the mean decrease in Gini index. For 
Regression, the 
first column is the mean decrease in accuracy and the second the mean 
decrease in MSE. If importance=FALSE, the last measure is 
still returned 
as a vector.'

So as far as I can see, you would have to change randomForest itself 
that has to return some relevant values in order to calculate the 
criterion(s) you are interested in.

Best wishes,
Uwe Ligges






linuxkaffee at gmx.net wrote:

Hi,

I've a question about the RandomForest package.

The package allows the extraction of a variable importance 

measure. As far as

I could see from the documentation, the computation is 

based on the Gini index.

Do you know if this extraction can be also based on other 

criteria? In particular,

I'm interested in the info gain criterion.

Best regards,
Chris
--