dividing columns in a list in R

问题

I am trying to add a column in a data.frame and have the output of that new column be the division of column 3 by column 2, here is an example:

mylist <- list( a=c(0,1,2),b=c(0,2,3),c=c(0,4,5))

this returns:

$a
[1] 0 1 2

$b
[1] 0 2 3

$c
[1] 0 4 5

I would like to return:

$a
[1] 0 1 2 2

$b
[1] 0 2 3 1.5

$c
[1] 0 4 5 1.25

Please help

回答1:

We can loop through the list with lapply, divide the 3rd element by the 2nd and concatenate with the original vector

lapply(mylist, function(x) c(x, x[3]/x[2]))

回答2:

We can use the purrr package.

library(purrr)

map(mylist, ~c(., .[3]/.[2]))
$a
[1] 0 1 2 2

$b
[1] 0.0 2.0 3.0 1.5

$c
[1] 0.00 4.00 5.00 1.25

来源：https://stackoverflow.com/questions/46712423/dividing-columns-in-a-list-in-r