[R] Taking the sum of only some columns of a data frame

[William Dunlap]

> dat <- data.frame(Group=LETTERS[1:5], X=1:5, Y=11:15)
> pos <- c(2,3)
> rbind(dat, Sum=lapply(seq_len(ncol(dat)), function(i) if (i %in% pos) sum(dat[,i]) else NA_real_))
    Group  X  Y
1       A  1 11
2       B  2 12
3       C  3 13
4       D  4 14
5       E  5 15
Sum  <NA> 15 65
> str(.Last.value)
'data.frame':   6 obs. of  3 variables:
 $ Group: Factor w/ 5 levels "A","B","C","D",..: 1 2 3 4 5 NA
 $ X    : int  1 2 3 4 5 15
 $ Y    : int  11 12 13 14 15 65
Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, Mar 31, 2017 at 9:20 AM, Bruce Ratner PhD <br at dmstat1.com> wrote:
> Hi R'ers:
> Given a data.frame of five columns and ten rows.
> I would like to take the sum of, say, the first and third columns only.
> For the remaining columns, I do not want any calculations, thus rending their "values" on the "total" row blank. The sum/total row is to be combined to the original data.frame, yielding a data.frame with five columns and eleven rows.
>
> Thanks, in advance.
> Bruce
>
>
> ______________
> Bruce Ratner PhD
> The Significant Statistician™
>
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