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

Doran, Harold HDoran at air.org
Fri Mar 31 18:33:57 CEST 2017

I do not believe this can be done in one step

dat <- data.frame(matrix(rnorm(50), 5))

 pos <- c(1,3)
res <-  apply(dat[, pos], 2, sum)

 x <- numeric(5)
 x[pos] <- res


-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Bruce Ratner PhD
Sent: Friday, March 31, 2017 12:20 PM
To: r-help at r-project.org
Subject: [R] Taking the sum of only some columns of a data frame

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 Ratner PhD
The Significant Statistician™

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