Home How do you rename the elements of a list when they are nested within another list using R's purrr package?

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How do you rename the elements of a list when they are nested within another list using R's purrr package?

February 10, 2022

The NBER dates recessions by their peak and trough. The json version of the data is here. A simple version looks like this:

list_old <- list(list(peak = "", trough = "1854-12-01"), list(peak = "1857-06-01", trough = "1858-12-01"))

In order for plotBands to be displayed in the highcharter package, the lists must be renamed so that "peak" becomes "start" and "trough" becomes "end". The resulting list would look like this:

list_new <- list(list(start = "", end = "1854-12-01"), list(start = "1857-06-01", end = "1858-12-01"))

Is there a way to achieve this using the tidyverse in R? (I’ve been looking in the purrr package.)

>Solution :

You can just use lapply to rename each list.

lapply(list_old, \(x) {
  names(x) <- c("start", "end")
  x
  }
)
#> [[1]]
#> [[1]]$start
#> [1] ""
#> 
#> [[1]]$end
#> [1] "1854-12-01"
#> 
#> 
#> [[2]]
#> [[2]]$start
#> [1] "1857-06-01"
#> 
#> [[2]]$end
#> [1] "1858-12-01"

You could use purrr::map() if you’d rather a tidy solution. If using purrr, from @Donald Seinen’s comment, can also use set_names()

library(purrr)

map(
  list_old,
  set_names,
  c("start", "end")
)
#> [[1]]
#> [[1]]$start
#> [1] ""
#> 
#> [[1]]$end
#> [1] "1854-12-01"
#> 
#> 
#> [[2]]
#> [[2]]$start
#> [1] "1857-06-01"
#> 
#> [[2]]$end
#> [1] "1858-12-01"