Hi Stephen,
Try out lapply(). It would help you loop through all data frames and sum.
Regards,
Vikash
On Thu, Oct 16, 2014 at 1:58 AM, Stephen HK Wong <hon...@stanford.edu>
wrote:
> Dear All,
>
> I have many 50 objects they are all dataframes. Each dataframe has many
> rows and four column. I simply want to do an addition of 3rd and 4th column
> and save the result into 5th column. Since there are many dataframes, I
> don't want to do it one by one, is there a way to loop through all objects
> and perform the similar action ?
>
> One way I can think of is like this:
>
> for (i in 1:50){
> get(ls()[i])[,3]+get(ls()[i][,4]
> }
>
> But I don't know how to save the addition result back to 5th column of
> each dataframe.
>
>
> Many Thanks!
>
>
>
> Stephen HK Wong
>
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