how to change data type in data frame?

Here's one way:
temp <- as.matrix(trash)
temp[temp=='b'] <- 1
temp[temp=='a'] <- 0
temp <- as.data.frame(structure(as.numeric(temp), dim=dim(trash),
dimnames=dimnames(trash)))
temp
age typeI typeII
1   1     0      1
2   2     0      0
3   3     1      1
4   4     0      1
5   5     1      0

HTH,
Andy
From: Auston_Wei at mdanderson.org

Hi, list,

suppose i have such a data frame:

trash <- 
data.frame(cbind(seq(1:5),c('a','a','b','a','b'),c('b','a','b'
,'b','a')))
names(trash) <- c('age','typeI','typeII')

and I want to change all 'a's to be 0 and 'b's to be 1. 

temp <- as.matrix(trash)
temp[temp=='a'] <- 0
temp[temp=='b'] <- 1
temp <- data.frame(temp)

the problem was that temp$typeI and temp$typeII were still factors, 
whereas I want numeric type. How can I make it?

Thanks,
Auston
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Liaw, Andy <andy_liaw <at> merck.com> writes:
Here's one way:

temp <- as.matrix(trash)
temp[temp=='b'] <- 1
temp[temp=='a'] <- 0
temp <- as.data.frame(structure(as.numeric(temp), dim=dim(trash),
dimnames=dimnames(trash)))
temp
  age typeI typeII
1   1     0      1
2   2     0      0
3   3     1      1
4   4     0      1
5   5     1      0

HTH,
Andy

Thank you very much, Andy. It works. Yet another question, what if I want to 
keep age as a factor? Is it possible?

thank you,
Auston