use %>% with replacement functions like colnames()<-

Question

How can I use the pipe operator to pipe into replacement function like colnames()<- ?

Here's what I'm trying to do:

library(dplyr) averages_df <-     group_by(mtcars, cyl) %>%    summarise(mean(disp), mean(hp)) colnames(averages_df) <- c("cyl", "disp_mean", "hp_mean") averages_df  # Source: local data frame [3 x 3] #  #   cyl disp_mean   hp_mean # 1   4  105.1364  82.63636 # 2   6  183.3143 122.28571 # 3   8  353.1000 209.21429 

But ideally it would be something like:

averages_df <-    group_by(mtcars, cyl) %>%   summarise(mean(disp), mean(hp)) %>%   add_colnames(c("cyl", "disp_mean", "hp_mean")) 

Is there a way to do this without writing a specialty function each time?

The answers here are a start, but not exactly my question: Chaining arithmetic operators in dplyr

Answer 1

You could use colnames<- or setNames (thanks to @David Arenburg)

group_by(mtcars, cyl) %>%   summarise(mean(disp), mean(hp)) %>%   `colnames<-`(c("cyl", "disp_mean", "hp_mean"))   # or   # `names<-`(c("cyl", "disp_mean", "hp_mean"))   # setNames(., c("cyl", "disp_mean", "hp_mean"))   #   cyl disp_mean   hp_mean # 1   4  105.1364  82.63636 # 2   6  183.3143 122.28571 # 3   8  353.1000 209.21429 

Or pick an Alias (set_colnames) from magrittr:

library(magrittr) group_by(mtcars, cyl) %>%   summarise(mean(disp), mean(hp)) %>%   set_colnames(c("cyl", "disp_mean", "hp_mean")) 

dplyr::rename may be more convenient if you are only (re)naming a few out of many columns (it requires writing both the old and the new name; see @Richard Scriven's answer)