R help - Nov 2009 - Outputing multilple subsets

Hi Rusers,
  I hope to divide the original dataset into several subsets and output
these multilple datasets. But errors appeared in my loops. See example.
######
a<-c(1:10)
b<-c(rep(1,3),rep(2,3),rep(3,4))
c<-data.frame(a,b)  #c is the example data
num<-c(unique(b))
# I hope to get the subsets c_1.csv,c_2.csv and c_3.csv
#Errors
for (i in num)  {
   c_num<-c[c$b==num,]
   write.csv(c_num,file="c:/c_num.csv")
}

Warning messages:
1: In c$b == num :
  longer object length is not a multiple of shorter object length
2: In c$b == num :
  longer object length is not a multiple of shorter object length
3: In c$b == num :
  longer object length is not a multiple of shorter object length
  I think the problem should be file="c:/c_num.csv", anybody has ever
met
this problem?
  Thanks very much.
-----------------
Jane Chang
Queen's

	[[alternative HTML version deleted]]

Have you considered using split?

-Ista

On Sun, Nov 8, 2009 at 7:23 PM, rusers.sh <rusers.sh at gmail.com>
wrote:
> Hi Rusers,
> ?I hope to divide the original dataset into several subsets and output
> these multilple datasets. But errors appeared in my loops. See example.
> ######
> a<-c(1:10)
> b<-c(rep(1,3),rep(2,3),rep(3,4))
> c<-data.frame(a,b) ?#c is the example data
> num<-c(unique(b))
> # I hope to get the subsets c_1.csv,c_2.csv and c_3.csv
> #Errors
> for (i in num) ?{
> ? c_num<-c[c$b==num,]
> ? write.csv(c_num,file="c:/c_num.csv")
> }
>
> Warning messages:
> 1: In c$b == num :
> ?longer object length is not a multiple of shorter object length
> 2: In c$b == num :
> ?longer object length is not a multiple of shorter object length
> 3: In c$b == num :
> ?longer object length is not a multiple of shorter object length
> ?I think the problem should be file="c:/c_num.csv", anybody has
ever met
> this problem?
> ?Thanks very much.
> -----------------
> Jane Chang
> Queen's
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org

On Nov 8, 2009, at 7:23 PM, rusers.sh wrote:
> for (i in num)  {
>   c_num<-c[c$b==num,]
>   write.csv(c_num,file="c:/c_num.csv")
> }
>
> Warning messages:
> 1: In c$b == num :
>  longer object length is not a multiple of shorter object length
This is because you're comparing column b to the entire vector of  
numbers (num), not the current number in the iteration (i).  The first  
line of the loop should be "c_num<-c[c$b==i,]".

 From a style point of view, I'd use "n" as my variable, since
"i" is
too commonly used as an integer index.

Also, you will be overwriting the same file, called "c_num.csv", on  
each iteration.

You should try something more like:

for (n in num) {
   c.n <- c[c$b==n,]
   write.csv(c.n, file=paste("c:/c_", n, ".csv",
sep="")
}

I hope that helps.

Cheers,
Johann Hibschman