R help - Jan 2007 - creating a list of lists

Hello,

I'm trying to create a series of randomForest objects, basically in a  
loop like this:

forests <- list();

for (level in 1:10) {

          # do some other things here

	# create a random forest
	forest <- randomForest(
		x = x.level,
		y = z.level,
		ntree = trees
		);

	forests <- c(forests, forest);

	}


But instead of creating a list of 10 forests, this creates a list of  
180 elements, 18 for each forest.  Is there a way to create a list of  
randomForest objects for use later on in code like:

for (forest in forests) {
         values <- predict(forest, data);
         # do things with these predicted values
         }

Sincerely,
Paul

change
 forests <- c(forests, forest);
into
 forests[[level]] <- forest



On 1/6/07, Paul Boutros <paul.boutros at utoronto.ca>
wrote:
> Hello,
>
> I'm trying to create a series of randomForest objects, basically in a
> loop like this:
>
> forests <- list();
>
> for (level in 1:10) {
>
>           # do some other things here
>
>         # create a random forest
>         forest <- randomForest(
>                 x = x.level,
>                 y = z.level,
>                 ntree = trees
>                 );
>
>         forests <- c(forests, forest);
>
>         }
>
>
> But instead of creating a list of 10 forests, this creates a list of
> 180 elements, 18 for each forest.  Is there a way to create a list of
> randomForest objects for use later on in code like:
>
> for (forest in forests) {
>          values <- predict(forest, data);
>          # do things with these predicted values
>          }
>
> Sincerely,
> Paul
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Weiwei Shi, Ph.D
Research Scientist
GeneGO, Inc.

"Did you always know?"
"No, I did not. But I believed..."
---Matrix III

Howabout using 'lapply'?

forest <- lapply(1:10, function(level) {
  # do some other things here
  # create and return a random forest
   randomForest(x = x.level, y = z.level, ntree = trees)
})

# give meaningful names
names(forest) <- paste("level", 1:10, sep = "_")
 
Paul Boutros wrote:
> Hello,
>
> I'm trying to create a series of randomForest objects, basically in a  
> loop like this:
>
> forests <- list();
>
> for (level in 1:10) {
>
>           # do some other things here
>
> 	# create a random forest
> 	forest <- randomForest(
> 		x = x.level,
> 		y = z.level,
> 		ntree = trees
> 		);
>
> 	forests <- c(forests, forest);
>
> 	}
>
>
> But instead of creating a list of 10 forests, this creates a list of  
> 180 elements, 18 for each forest.  Is there a way to create a list of  
> randomForest objects for use later on in code like:
>
> for (forest in forests) {
>          values <- predict(forest, data);
>          # do things with these predicted values
>          }
>
> Sincerely,
> Paul
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>   

-- 

Eric Archer, Ph.D.
NOAA-SWFSC
8604 La Jolla Shores Dr.
La Jolla, CA 92037
858-546-7121,7003(FAX)
eric.archer at noaa.gov


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