Flux Flux - 2 months ago 22
R Question

dplyr: select column names containing white space

df <- structure(list(`a a` = 1:3, `a b` = 2:4), .Names = c("a a", "a b"
), row.names = c(NA, -3L), class = "data.frame")


and the data looks like

a a a b
1 1 2
2 2 3
3 3 4


Following call to select

select(df, 'a a')


gives

Error in abs(ind[ind < 0]) :
non-numeric argument to mathematical function


How can I select "a a" and/or rename it to something without space using
select
? I know the following approaches:


  1. names(df)[1] <- "a"

  2. select(df, a=1)

  3. select(df, ends_with("a"))



but if I am working on a large data set, how can I get an exact match without knowing the index numer or similar column names?

Answer

You may select the variable by using backticks.

select(df, `a a`)
#   a a
# 1   1
# 2   2
# 3   3

However, if your main objective is to rename the column, you may use rename in plyr package, in which you can use both "" and ``.

rename(df, replace = c("a a" = "a"))
rename(df, replace = c(`a a` = "a"))

Or in base R:

names(df)[names(df) == "a a"] <- "a"

For a more thorough description on the use of various quotes, see ?Quoutes. The 'Names and Identifiers' section is especially relevant here: "other [syntactically invalid] names can be used provided they are quoted. The preferred quote is the backtick". See also ?make.names about valid names.

See also this post about renaming in dplyr

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