[R] Isolating a column within a loop

Steve Murray smurray444 at hotmail.com
Mon Feb 1 14:49:47 CET 2010

Dear all,

I am trying to calculate the mean of one column for many data frames. The code I am using is as follows:

> for (i in seq(nrow(index))) {
        assign(paste(model, "_mean_",index$year[i], index$month[i], sep=''),
              mean(get(paste(model, index$year[i], index$month[i], "[,3]", sep=''))))

Error in get(paste(model, index$year[i], index$month[i], "[,3]", sep = "")) : 
  object 'cccma207101[,3]' not found

The error message I'm getting is strange, because this object does exist:

 num [1:61538] 0.687 2.661 0 0 0 ...

If I leave the "[,3]" out of the loop, the code seems to work fine - so I'm isolating this as the cause of the problem for now.

My question is therefore, how can I use the above code to extract column three from each of the (360) data frames?

Many thanks for any help offered,


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