CODEWITHSUNDEEP
rtidyversepurrr
Jeremy K.
Jeremy K.

Reputation: 1792

map() model output to a dataframe

I've been using map() to calculate and extract certain statistics from multiple lm() models.

To give a reproducible example, using the mtcars dataset, I start with an input vector of formulae to be estimated using lm() models:

library(tidyverse)
df <- mtcars
input_char <- c("mpg ~ disp",
                "mpg ~ disp + hp")
input_formula <- map(input_char, formula)

I've then got a function that calculates and extracts the relevant statistics for each model. For simplicity and reproducibility, here's a simplified function that just extracts the R-squared of the model.

get_rsquared <- function(a_formula) {
  model1 <- lm(a_formula, data = df)
  rsquared <- summary(model1)$r.squared
  c(model = a_formula, rsquared = rsquared)
}

I've then used map to iterate through the formulae and extract the R-squared from each model. 

models <- map(input_formula, get_rsquared)
models

which gives the output:

[[1]]
[[1]]$model
mpg ~ disp
<environment: 0x7f98987f4000>

[[1]]$rsquared
[1] 0.7183433


[[2]]
[[2]]$model
mpg ~ disp + hp
<environment: 0x7f98987f4000>

[[2]]$rsquared
[1] 0.7482402

My question is regarding the output being a list.

Is there a simple way to make the output a dataframe?

My desired output is:


#>             model  rsquared
#> 1      mpg ~ disp 0.7183433
#> 2 mpg ~ disp + hp 0.7482402

Upvotes: 0

Views: 536

Answers (1)

lroha
lroha

Reputation: 34441

Keep the formulas as character strings and use as.formula() as part of the the get_rsquared() function as it's easier to work with them as character strings than formula objects.

library(purrr)
library(dplyr)

df <- mtcars
input_char <- c("mpg ~ disp",
                "mpg ~ disp + hp")

get_rsquared <- function(a_formula) {
  model1 <- lm(as.formula(a_formula), data = df)
  rsquared <- summary(model1)$r.squared
  list(model = a_formula, rsquared = rsquared)
}

map_df(input_char, get_rsquared)

# A tibble: 2 x 2
  model           rsquared
  <chr>              <dbl>
1 mpg ~ disp         0.718
2 mpg ~ disp + hp    0.748

Upvotes: 2

Related Questions