CODEWITHSUNDEEP
rlist
Jcarl
Jcarl

Reputation: 161

Multiply list of lists at different levels in R

I would like to multiply the numeric values two levels deep in a list by the values one level deep in another list in R. For example, consider the following:

library(tidyverse)
library(purrr)
library(dplyr)

weights <- list(a = list(1, 3, 8), b = list(2, 4), c = list(5, 2, 8, 0.5)) 
multiplier <- list(0.5, 0.25, 0.10)

This is the basic idea of what I'd like to do, but this does not work.....

result <- weights * multiplier

I would like to produce a list of lists with the same structure as the list titled "weights" but with each variable multiplied by the value in the "multiplier" list.

My desired result is:

result <- list(a = list(0.5, 1.5, 4), b = list(0.5, 1), c = list(0.5, 0.2, 0.8, 0.05))

I feel like this should be a relatively easy thing to do, but I can't seem to figure it out.

Upvotes: 1

Views: 290

Answers (1)

akrun
akrun

Reputation: 887148

We can use map2 to loop over the list, and as 'weights' is a nested list, unlist it, multiply with each corresponding element from 'multiplier' list, and relist it back to list

library(purrr)
map2(weights, multiplier,  ~ relist(unlist(.x) * .y, skeleton = .x))

The similar option in base R is with Map

Map(function(x, y) relist(unlist(x) * y, skeleton = x), weights, multiplier)

Or another option is to stack it to a two column data.frame, and then do the multiplication after replicating to make lengths same and then relist

relist(with(stack(weights), values *
          rep(unlist(multiplier), table(ind))), weights)

Upvotes: 1

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