Converting two columns of a data frame to a named vector
RVectorDataframeCoercionR Problem Overview
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")
R Solutions
Solution 1 - R
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 - R
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 - R
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$crit))
Solution 4 - R
Here is a very general, easy, tidy way:
library(dplyr)
iris %>%
pull(Sepal.Length, Species)
The first argument is the values, the second argument is the names.
Solution 5 - R
For variety, try split
and unlist
:
unlist(split(as.character(dd$name), dd$crit))
# a b c d
# "Alpha" "Beta" "Caesar" "Doris"
Solution 6 - R
There's also a magrittr
solution to this via the exposition pipe (%$%
):
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"
.