Dear R's
I'm trying to use specific rather than random cross-validation groups
in mvpart.
The man page says:
xval Number of cross-validations or vector defining cross-validation groups.
And I found this reply to the list by Terry Therneau from 2006
The rpart function allows one to give the cross-validation groups explicitly.
So if the number of observations was 10, you could use
> rpart( y ~ x1 + x2, data=mydata, xval=c(1,1,2,2,3,3,1,3,2,1))
which causes observations 1,2,7, and 10 to be left out of the first xval
sample, 3,4, and 9 out of the second, etc.
Terry Therneau
I can't see how this string of values, c(1,1,2,2,3,3,1,3,2,1), codes
for observations 1,2,7,10 being left out of the 1st and so on.
Can anyone fill me in please?
Thanks,
andydol...@gmail.com
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