Error of Cross Validation

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You real error was this:

Error in pre[sam[[j]], i] <- predict(fit, data = dat[sam[[j]], ]) :
  number of items to replace is not a multiple of replacement length

Take a look at the statement and you will see that 'predict' is
returning 100 values and you are trying to store it into only 10 rows
(that is what sam[[j]] is).  You need to rethink what you are trying
to do.  Let me ask my favorite question:  what is the problem you are
trying to solve?
error in pre[sam[[j]], i] <- predict(fit, data = dat[sam[[j]], ]) :

Yao Zhu
Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China

2011/6/20 Jim Holtman <jholtman at gmail.com>
what was the error?

Sent from my iPad

On Jun 20, 2011, at 1:34, zhu yao <mailzhuyao at gmail.com> wrote:

Dear R users:

Recently, I tried to write a program to calculate cross-validated
predicted
value.
My sources are as follows. However, the R reported an error.
Could you please check the sources? Thanks.

set.seed(100)
x<-rnorm(100)
y<-sample(rep(0:1,50),replace=T)
dat<-data.frame(x,y)

library(rms)

fito<-lrm(y~x)
preo<-predict(fito)

pre<-matrix(NA,nrow=100,ncol=200)

for (i in 1:200)
{
sam<-sample(1:nrow(dat))
sam<-split(sam,1:10)
for (j in 1:10)
{
fit<-lrm(y~x,data=dat[-sam[[j]],])
pre[sam[[j]],i]<-predict(fit,data=dat[sam[[j]],])
}
}

*Yao Zhu*
*Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China*

? ?[[alternative HTML version deleted]]

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Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?