dplyr on subset of columns while keeping the rest of the data.frame

Question

I am trying to use dplyr to apply a function to a subset of columns. However, in contrast to the code per below, I am trying to implement this while keeping all columns in the data-frame. Currently, the resulting data-frame only keeps the selected columns. I can use a remove-and-cbind construction to merge these columns back into the original dataframe, but I was wondering if there is a way to do this directly in dplyr? I have tried to move the select function inside the mutate function, but was not able to make this work yet.

require(dplyr)
Replace15=function(x){ifelse(x<1.5,1,x)}
dg <- iris %>%
  dplyr::select(starts_with("Petal")) %>%
  mutate_each(funs(Replace15))  
dg

> dg
Source: local data frame [150 x 2]

   Petal.Length Petal.Width
1           1.0           1
2           1.0           1
3           1.0           1
4           1.5           1
5           1.0           1
6           1.7           1
7           1.0           1
8           1.5           1
9           1.0           1
10          1.5           1

Maybe just iris %>% mutate_each(funs(Replace15), starts_with("Petal")) ? — aosmith
You can also define your function in terms of the built-in replace function. ifelse can be slow, if that's a concern of yours. stackoverflow.com/q/16275149/1191259 — Frank

Nick Kennedy Nick Kennedy · Accepted Answer · 2015-06-25T15:46:55

dg <- iris %>% mutate_each(funs(Replace15), matches("^Petal"))

Alternatively (as posted by @aosmith) you could use starts_with. Have a look at ?select for the other special functions available within select, summarise_each and mutate_each.

dplyr on subset of columns while keeping the rest of the data.frame

2 Answers