Converting two columns of a data frame to a named vector

Question

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")

Solution 1

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)

Solution 2

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.

Solution 3

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))

Solution 4

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.

Solution 5

For variety, try split and unlist:

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

View more solutions

Comments

[Roland]

It should be pointed out that this makes duplicated names unique by appending a number to them. It's also not very efficient with big vectors.

[HowYaDoing]

Thank you John! I am amazed that after years of using the tidyverse I still learn about functions that are so useful. I wish I knew about this a long time ago. I guess I'm always a student.

[merv]

Very neat. Probably will become my goto once it goes live.

[ChrKoenig]

should be the top answer in 2021

[acvill]

For anyone coming to this post asking the inverse question - How do I convert a named vector to a two-column data frame? - the answer is tibble::enframe()