[R] Iterations

[Erik Iverson]

If you read the help page, ?for, you might have seen under "Value", that

      'for', 'while' and 'repeat' return the value of the last
      expression evaluated (or 'NULL' if none was), invisibly.

So if you want to see the values, print() them.

In general, from the first part of your message, it looks like you're 
trying to run some analysis on different subgroups of your data.

You may want to try the functions tapply, by, aggregate, ave, etc., for 
this purpose rather than using 'for' loops.

Best,
Erik Iverson


rkevinburton at charter.net wrote:
> I have a command that reads in some data:
> 
> x <- read.csv("Sales2007.dat", header=TRUE)
> 
> Then I try to organize the data:
> 
> sc <- split(x, list(x$Category, x$SubCategory), drop=TRUE)
> 
> Then I want to iterate through the data. I was able to get the following to run on the R console:
> 
> for(i in 1:length(sc))
> {
>     sum(sc[[i]]$Quantity)
> }
> 
> But notiing is primted on the console. I find that:
> 
> for(i in 1:100)
> {
>     i
> }
> 
> Also does't output anything? I am probably making a wrong assumption here. Why desn't the loop seem to output anyything?
> 
> Thank you.
> 
> Kevin
> 
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