[R] Using sample to create Training and Test sets

[Liaw, Andy]

Here's one possibility:

idx <- sample(nrow(acc))
training <- acc[idx[1:400], ]
testset <- acc[-idx[1:400], ]

Andy

From: Chris Arthur
> 
> Forgive the newbie question, I want to select random rows from my 
> data.frame to create a test set (which I can do) but then I want to 
> create a training set using whats left over.
> 
> Example code:
> acc <- read.table("accOUT.txt", header=T, sep = ",", row.names=1)
> #select 400 random rows in data
> training <- acc[sample(1:nrow(acc), 400, replace=TRUE),]
> 
> #try to get whats left of acc not in training
> testset <- acc[-training, ]
> Fails with the following error....
> Error: invalid subscript type
> In addition: Warning message:
> - not meaningful for factors in: Ops.factor(left)
> 
> I then try.
> testset <- acc[!training, ]
> Which gives me the warning message
> ! not meaningful for factors in: Ops.factor(left)
> And if i look at testset It is 400 rows of NA's ... which 
> clearly isn't 
> right.
> 
> Can anyone tell me what I'm doing wrong.
> 
> Thanks in advance
> 
> Chris
> 
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