R help - Mar 2014 - randomForest warning: The response has five or fewer unique values. Are you sure you want to do regression?

Hello everyone,

 

Im relatively new to R and new to the randomForest package and have scoured
the archives for help with no luck. I am trying to perform a regression on a
set of predictors and response variables to determine the most important
predictors. I have 100 response variables collected from 14 sites and 8
predictor variables from the same 14 sites. I run the code to perform the
randomForest  regression given by Pitcher et al 2011   (
http://gradientforest.r-forge.r-project.org/biodiversity-survey.pdf ). 

 

However, after running the code I get the warning:

 

" In randomForest.default(m, y, ...) :

  The response has five or fewer unique values.  Are you sure you want to do
regression?"

 

And it produces a set of 500 regression trees for each of 3 species only
when the number of species in the response file is 100. I noticed that in
the example by Pitcher they get 500 trees from only 90 species even though
they input 110 species in the response data.

 

Why am I getting the warning/how do I solve it, and why is randomForest
producing trees for only 3 species when I am looking at 100 species
(response variables)?

 

Many thanks

 

Sean

 


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