R help - May 2010 - randomforests - how to classify

Hi,

I'm experimenting with random forests and want to perform a binary
classification task. 
I've tried some of the sample codes in the help files and things run, but I
get a message to the effect 'you don't have very many unique values in
the
target - are you sure you want to do regression?' (sorry, don't know
exact
message but r is busy now so can't check).


In reading the help files I see 2 examples, one for classification and one
for regression. To the uninformed - these don't seem much different to each
other. How does rf know to do regression or classification?

## Classification:
##data(iris)
set.seed(71)
iris.rf <- randomForest(Species ~ ., data=iris, importance=TRUE,
                        proximity=TRUE)


## Regression:
## data(airquality)
set.seed(131)
ozone.rf <- randomForest(Ozone ~ ., data=airquality, mtry=3,
                         importance=TRUE, na.action=na.omit)


My target variable only has 2 values - why does it want to do regression?
I've entered code just like that in the classification example above. Also
when it asks me 'are you sure you want to do regression' - how do I say
'NO,
do classification please'?




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use (as.factor(target) ~., data =your data, ...)





On Tue, May 4, 2010 at 12:07 PM, pdb <philb@philbrierley.com> wrote:
>
> Hi,
>
> I'm experimenting with random forests and want to perform a binary
> classification task.
> I've tried some of the sample codes in the help files and things run,
but I
> get a message to the effect 'you don't have very many unique values
in the
> target - are you sure you want to do regression?' (sorry, don't
know exact
> message but r is busy now so can't check).
>
>
> In reading the help files I see 2 examples, one for classification and one
> for regression. To the uninformed - these don't seem much different to
each
> other. How does rf know to do regression or classification?
>
> ## Classification:
> ##data(iris)
> set.seed(71)
> iris.rf <- randomForest(Species ~ ., data=iris, importance=TRUE,
>                        proximity=TRUE)
>
>
> ## Regression:
> ## data(airquality)
> set.seed(131)
> ozone.rf <- randomForest(Ozone ~ ., data=airquality, mtry=3,
>                         importance=TRUE, na.action=na.omit)
>
>
> My target variable only has 2 values - why does it want to do regression?
> I've entered code just like that in the classification example above.
Also
> when it asks me 'are you sure you want to do regression' - how do I
say
> 'NO,
> do classification please'?
>
>
>
>
> --
> View this message in context:
>
http://r.789695.n4.nabble.com/randomforests-how-to-classify-tp2126166p2126166.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org 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.
>


-- 
Sincerely,
Changbin
--

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