CODEWITHSUNDEEP
r
Jamie
Jamie

Reputation: 553

Dplyr: Count number of observations in group and summarise?

Im wondering if there is a more elegant way to perform this.

Right now, I am grouping all observations by Species. Then I summarize the median values.

median <- iris  %>% 
  group_by(Species) %>% 
  summarise(medianSL = median(Sepal.Length),
            medianSW = median(Sepal.Width),
            medianPL = median(Petal.Length),
            medianPW = median(Petal.Width))

I also wanted a column (n) that shows the amount of flowers in each row:

median_n <- iris  %>% 
  group_by(Species) %>% 
   tally()

Can I combine these two code chunks? So that way the above code chunk will generate a table with the median lengths AND the total n for each row?

Upvotes: 0

Views: 294

Answers (1)

akrun
akrun

Reputation: 886938

We may use across in summarise to loop over the numeric columns to get the median as well as create a frequency count with n() outside the across

library(dplyr)
library(stringr)
iris  %>% 
  group_by(Species) %>% 
   summarise(across(where(is.numeric), 
    ~ median(.x, na.rm = TRUE),
     .names = "median{str_remove_all(.col, '[a-z.]+')}"),
    n = n(), .groups = "drop")

-output

# A tibble: 3 × 6
  Species    medianSL medianSW medianPL medianPW     n
  <fct>         <dbl>    <dbl>    <dbl>    <dbl> <int>
1 setosa          5        3.4     1.5       0.2    50
2 versicolor      5.9      2.8     4.35      1.3    50
3 virginica       6.5      3       5.55      2      50

Upvotes: 4

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