CODEWITHSUNDEEP
rvectordataframecoercion
Stefan F
Stefan F

Reputation: 2753

Converting two columns of a data frame to a named vector

I need to convert a multi-row two-column data.frame to a named character vector. My data.frame would be something like:

dd = data.frame(crit = c("a","b","c","d"), 
                name = c("Alpha", "Beta", "Caesar", "Doris")
                )

and what I actually need would be:

whatiwant = c("a" = "Alpha",
              "b" = "Beta",
              "c" = "Caesar",
              "d" = "Doris")

Upvotes: 105

Views: 35165

Answers (6)

stevec
stevec

Reputation: 52268

Here is a very general, easy, tidy way:

library(dplyr)

iris %>%
  pull(Sepal.Length, Species)

The first argument is the values, the second argument is the names.

Upvotes: 36

merv
merv

Reputation: 76760

There's also a magrittr solution to this via the exposition pipe (%$%):

library(magrittr)

dd %$% set_names(as.character(name), crit)

Minor advantage over tibble::deframe is that one doesn't have to have exactly a two-column frame/tibble as argument (i.e., avoid a select(value_col, name_col) %>%).

Note that the magrittr::set_names versus base::setNames is exchangeable. I simply prefer the former since it matches "set_(col|row)?names".

Upvotes: 3

John Waller
John Waller

Reputation: 2507

You can also use deframe(x) from the tibble package for this.

tibble::deframe()

It converts the first column to names and second column to values.

Upvotes: 81

alexwhan
alexwhan

Reputation: 16026

You can make a vector from dd$name, and add names using names(), but you can do it all in one step with structure():

whatiwant <- structure(as.character(dd$name), names = as.character(dd$crit))

Upvotes: 27

A5C1D2H2I1M1N2O1R2T1
A5C1D2H2I1M1N2O1R2T1

Reputation: 193517

For variety, try split and unlist:

unlist(split(as.character(dd$name), dd$crit))
#        a        b        c        d 
#  "Alpha"   "Beta" "Caesar"  "Doris"

Upvotes: 8

Roland
Roland

Reputation: 132706

Use the names function:

whatyouwant <- as.character(dd$name)
names(whatyouwant) <- dd$crit

as.character is necessary, because data.frame and read.table turn characters into factors with default settings.

If you want a one-liner:

whatyouwant <- setNames(as.character(dd$name), dd$crit)

Upvotes: 102

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