CODEWITHSUNDEEP
r
Venkat Chidambaram
Venkat Chidambaram

Reputation: 73

What is the use of .$ in R

What does the .$avg signify?

conditional_avg <- galton_heights %>% 
                         filter(round(father) == 72) %>%
                         summarize(avg = mean(son)) %>%
                         .$avg

Upvotes: 0

Views: 632

Answers (1)

akrun
akrun

Reputation: 887951

The .$ is used to extract the column avg as a vector. Here, . represents the data coming from the lhs of the %>%. It can be vector or list or data.frame. In this case, it is a data.frame with a single column 'avg'. We use $ or [[ to extract the column as a vector. There is also a convenient function pull to do this

library(tidyverse)
galton_heights %>%
    filter(round(father) == 72) %>%
    summarize(avg = mean(son))  %>%     
    pull(avg)

As a reproducible example, using data(mtcars), if we don't extract the 'avg' column, it will be a data.frame with a single column

mtcars %>%
   summarise(avg = mean(hp)) %>% 
   str
# 'data.frame': 1 obs. of  1 variable:
#$ avg: num 147

Extracting the column returns as a vector.

mtcars %>% 
     summarise(avg = mean(hp)) %>% 
     .$avg
#[1] 146.6875

mtcars %>% 
     summarise(avg = mean(hp)) %>%
     pull
#[1] 146.6875

Upvotes: 3

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