C8H10N4O2 C8H10N4O2 - 1 month ago 34
R Question

R dplyr: rename variables using string functions

(Somewhat related question: Enter new column names as string in dplyr's rename function)

In the middle of a

dplyr
chain (
%>%
), I would like to replace multiple column names with functions of their old names (using
tolower
or
gsub
, etc.)

library(tidyr); library(dplyr)
data(iris)
# This is what I want to do, but I'd like to use dplyr syntax
names(iris) <- tolower( gsub("\\.", "_", names(iris) ) )
glimpse(iris, 60)
# Observations: 150
# Variables:
# $ sepal_length (dbl) 5.1, 4.9, 4.7, 4.6, 5.0, 5.4, 4.6,...
# $ sepal_width (dbl) 3.5, 3.0, 3.2, 3.1, 3.6, 3.9, 3.4,...
# $ petal_length (dbl) 1.4, 1.4, 1.3, 1.5, 1.4, 1.7, 1.4,...
# $ petal_width (dbl) 0.2, 0.2, 0.2, 0.2, 0.2, 0.4, 0.3,...
# $ species (fctr) setosa, setosa, setosa, setosa, s...

# the rest of the chain:
iris %>% gather(measurement, value, -species) %>%
group_by(species,measurement) %>%
summarise(avg_value = mean(value))


I see
?rename
takes the argument
replace
as a
named character vector, with new names as values, and old names as names.


So I tried:

iris %>% rename(replace=c(names(iris)=tolower( gsub("\\.", "_", names(iris) ) ) ))


but this (a) returns
Error: unexpected '=' in iris %>% ...
and (b) requires referencing by name the data frame from the previous operation in the chain, which in my real use case I couldn't do.

iris %>%
rename(replace=c( )) %>% # ideally the fix would go here
gather(measurement, value, -species) %>%
group_by(species,measurement) %>%
summarise(avg_value = mean(value)) # I realize I could mutate down here
# instead, once the column names turn into values,
# but that's not the point
# ---- Desired output looks like: -------
# Source: local data frame [12 x 3]
# Groups: species
#
# species measurement avg_value
# 1 setosa sepal_length 5.006
# 2 setosa sepal_width 3.428
# 3 setosa petal_length 1.462
# 4 setosa petal_width 0.246
# 5 versicolor sepal_length 5.936
# 6 versicolor sepal_width 2.770
# ... etc ....

Answer

I think you're looking at the documentation for plyr::rename, not dplyr::rename. You would do something like this with dplyr::rename:

iris %>% rename_(.dots=setNames(names(.), tolower(gsub("\\.", "_", names(.)))))