r: can someone explain this dplyr code to me?

Question

Pretty straightforward question. Here is the code:

library(dplyr)
library(tidyr)

mtcars %>% group_by(gear) %>% select(hp, disp) %>% 
summarise_all(funs(n=sum(!is.na(.)), mean=mean(.,na.rm=T))) %>% 
gather(variable, value, -gear) %>% 
arrange(gear, sub('_.*', '', variable), sub('.*_', '', variable)) %>%
separate(variable, into = c('var', 'metric'), '_')

I understand everything up to the gather statement. I'm not familiar with these functions and the help files are not very useful.

Can anyone walk me through this? I'd like to build a function around these commands, but I need to understand how this all works before doing that.

Answer 1

gather moves from "wide" format to long format, -gear means don't gather gear . gather puts the remaining columns into a single variable and value column.

arrange just sorts by gear, the sub statements are useless, you could change the arrange row to arrange(gear, variable) .

separate splits the variable column into two using _ as the delimiter