CODEWITHSUNDEEP
rdplyr
Paulina
Paulina

Reputation: 13

How to use dplyr's summarize(across( )) when the function returns a list and the data is grouped

I am trying to use dplyr's summarise(across()) with the MannKendall function (returns a list). I have no problem using it if I don't use group_by() but when I do I get an error. This is my code:

Preds %>% group_by(Municipality) %>% 
   summarise(across(where(is.numeric),~list(MannKendall(.) %>%tidy %>% select(p.value, statistic)))) %>%
   pivot_longer(everything()) %>%
   unnest(c(value))

Error: Can't combine Municipality and Yield . Yield is one of my variables and it is numeric This works but is not what I need:

Preds %>%  
   summarise(across(where(is.numeric),~list(MannKendall(.) %>%tidy %>% select(p.value, statistic)))) %>%
   pivot_longer(everything()) %>%
   unnest(c(value))

For a reproducible example:

iris %>%
   group_by(Species) %>%
   summarise(across(starts_with("Sepal"), ~list(MannKendall(.) %>%tidy %>% select(p.value, statistic)))) %>%
   pivot_longer(everything()) %>%
   unnest(c(value))

I think the problem is in trying to tidy the resulting dataframe containing lists in each column

Upvotes: 1

Views: 352

Answers (1)

andrew_reece
andrew_reece

Reputation: 21284

You can use unnest_longer():

library(tidyverse)
library(broom)
library(Kendall)

iris %>%
  group_by(Species) %>%
  summarise(across(starts_with("Sepal"), ~list(
    MannKendall(.) %>% 
      tidy %>% 
      select(p.value, statistic)))) %>%
  unnest_longer(Sepal.Length) %>%
  unnest_longer(Sepal.Width)

# A tibble: 3 x 3
  Species    Sepal.Length$p.value $statistic Sepal.Width$p.value $statistic
  <fct>                     <dbl>      <dbl>               <dbl>      <dbl>
1 setosa                   0.926     -0.0102               0.920    -0.0111
2 versicolor               0.0753    -0.178                0.400    -0.0859
3 virginica                0.750     -0.0326               0.226     0.124

Upvotes: 2

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