CODEWITHSUNDEEP
rdplyrpurrrbroom
Nazer
Nazer

Reputation: 3764

Extract residuals from models fit in purrr

I grouped my data and fit a model to each group and I would like to have the residuals for each group. I can see the residuals for each model with RStudio's viewer, but I cannot figure out how to extract them. Extracting one set of residuals can be done like diamond_mods[[3]][[1]][["residuals"]], but how do I use purrr to extract the set from every group (along with broom to end up with a nice tibble)?

Below is how far I've gotten: 

library(tidyverse)
library(purrr)
library(broom)


fit_mod <- function(df) {
  lm(price ~ poly(carat, 2, raw = TRUE), data = df)
}

diamond_mods <- diamonds %>%
  group_by(cut) %>%
  nest() %>%
  mutate(
    model = map(data, fit_mod),
    tidied = map(model, tidy)
    #resid = map_dbl(model, "residuals") #this was my best try, it doesn't work
  ) %>%
  unnest(tidied)

Upvotes: 1

Views: 902

Answers (2)

akrun
akrun

Reputation: 887223

With the devel version of dplyr, we can do this in condense after grouping by 'cut'

library(dplyr)
library(ggplot2)
library(broom)
diamonds %>%
   group_by(cut) %>%
   condense(model = fit_mod(cur_data()),
            tidied = tidy(model), 
            resid = model[["residuals"]])
# A tibble: 5 x 4
# Rowwise:  cut
#  cut       model  tidied           resid         
#  <ord>     <list> <list>           <list>        
#1 Fair      <lm>   <tibble [3 × 5]> <dbl [1,610]> 
#2 Good      <lm>   <tibble [3 × 5]> <dbl [4,906]> 
#3 Very Good <lm>   <tibble [3 × 5]> <dbl [12,082]>
#4 Premium   <lm>   <tibble [3 × 5]> <dbl [13,791]>
#5 Ideal     <lm>   <tibble [3 × 5]> <dbl [21,551]>

Upvotes: 1

lroha
lroha

Reputation: 34501

You were close - but you should use map() instead of map_dbl() as you need to return a list not a vector.

diamond_mods <- diamonds %>%
  group_by(cut) %>%
  nest() %>%
  mutate(
    model = map(data, fit_mod),
    tidied = map(model, tidy),
    resid = map(model, residuals)
  )

Upvotes: 1

Related Questions