Print data frame dimensions at each step of filtering

Question

I am using the tidyverse to filter out a dataframe and would like a print at each step of the dimensions (or nrows) of the intermediate objects. I thought I could simply use

Answer 1

The pipe %T>% from library magrittr was created just for this type of cases :

library(magrittr)
library(dplyr)
mtcars %>%
  filter(cyl > 4)     %T>% {print(dim(.))} %>%
  filter(am == 0)     %T>% {print(dim(.))} %>%
  filter(disp >= 200) %T>% {print(dim(.))}

Very easy to read and edit out in Rstudio using alt + selection if you ident as I do.

You can also use @hrbrmstr 's function here if you don't like brackets, except you won't need the last line.

---

Revisiting it months later here's an idea generalizing @hrbmst's solution so you can print pretty much what you want and return the input to carry on with the pipe.

library(tidyverse)
pprint <- function(.data,.fun,...){
  .fun <- purrr::as_mapper(.fun)
  print(.fun(.data,...))
  invisible(.data)
}

iris %>%
  pprint(~"hello")           %>%
  head(2)                    %>%
  select(-Species)           %>%
  pprint(rowSums,na.rm=TRUE) %>%
  pprint(~rename_all(.[1:2],toupper)) %>%
  pprint(dim)

# [1] "hello"
#    1    2 
# 10.2  9.5 
#   SEPAL.LENGTH SEPAL.WIDTH
# 1          5.1         3.5
# 2          4.9         3.0
# [1] 2 4