[R] how to put n and yprob on the tree plot ----- Re: what missed ----- CART

From: o ha wang <wyerliang_at_yahoo.com>
Date: Sun, 24 Feb 2008 13:28:09 -0800 (PST)


Thanks!    

  Yes, you were right. I loaded package 'tree'.    

  I tried 'tree' and 'rpart' respectively, it looks like results for regression tree are same, and very similar for classification tree. (more biref using 'rpart' than using 'tree').    

  But my problems are still not been solved using rpart.    

  1. how to put number (n, ie. class counts) and probability (yprob) on the plot for classification tree. There are only 0/1 on the plot. n and yprob can be seen using 'myfit' but not on the plot.
  2. The notation of Numbers are overlapped for regression tree.

  please see my rpart code:    

  library (rpart)
myfit <- rpart (y ~ x1 + x2 + x3 + x4 ) plot (myfit)); text (myfit, all= TRUE, cex=0.5, pretty=0) myfit
  summary(myfit)   

thanks, xiao yue       

Uwe Ligges <ligges_at_statistik.tu-dortmund.de> wrote:   

o ha wang wrote:
> Hi all,
>
> Can anyone who is familar with CART tell me what I missed in my tree code?
>
> library (MASS)
> myfit <- tree (y ~ x1 + x2 + x3 + x4 )

There is not function tree() in MASS. I guess you have loaded package "tree"?
Note that the author and maintainer of the tree package suggests to use package rpart instead.

> # tree.screens () # useless
> plot(myfit); text (myfit, all= TRUE, cex=0.5, pretty=0)
> # tile.tree (myfit, fgl$type) # useless
> # close.screen (all= TRUE) # useless
>
>
> My current tree plot resulted from above code shows as:
> 1. overlapped #s caused by unsuitable length of branch.
> 2. no misclassification rates: 'misclass.tree' only brings up the error of ' misclassification error rate is appropriate for factor responses only', but my response y is 0/1 data.

If you data is 0/1, you should make it a factor otherwise the cose will assume you want a regression rather than a classification tree.

> 3. Unsuitable location of notations: there are not two notation of splitting criteria on the two branches when a node is split, instead only one notation of splitting criteria is on the node location.

It indicates which items go into the left branch.

Uwe Ligges

>
> thanks,
> xiao yue
>
>
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