Quick example of purrr::nest analysis

purrr_example_iris.r

library(tidyverse)
g <- glimpse

g(iris)

dat <- iris %>% 
  nest(data = c(-Species))

dat$data[[1]]

lapply(dat$data, nrow)

map_int(dat$data, nrow)

dat2 <- dat %>% 
  mutate(nrow = map(data, nrow))

dat2 <- dat %>% 
  mutate(nrow = map_dbl(data, nrow))

dat3 <- dat2 %>% 
  mutate(lm = map(data, 
                  function(.x) lm(Sepal.Length ~ ., data = .x)))

dat3$lm[[1]]

dat4 <- dat3 %>% 
  mutate(pred = map(lm, ~predict(.x)))

dat4$pred[[1]]

== <- dat4 %>% 
  mutate(MAE = map2_dbl(data,pred, 
                    function(.x,.y) mean(abs(.x$Sepal.Length - .y))))

### All together
dat <- iris %>% 
  nest(data   = c(-Species)) %>% 
  mutate(nrow = map_dbl(data, nrow),
         lm   = map(data, function(.x) lm(Sepal.Length ~ ., data = .x)),
         pred = map(lm, function(.x) predict(.x)),
         MAE  = map2_dbl(data,pred, 
                        function(.x,.y) mean(abs(.x$Sepal.Length - .y))))


dat_plot <- dat %>% 
  select(-lm) %>% 
  unnest(cols = c(data, pred))