Extract number of rows from faceted ggplot

Question

Consider a faceted ggplot

plotdf <- data.frame(x = 1:21, 
                     y = 3*(1:21)+4, 
                     z = c(rep(1,3), rep(2,3), rep(3,3), rep(4         


        

Answer 1

Following up on @Aditya's answer, this is (as of ggplot 3.1.1):

library(magrittr)
gg_facet_nrow_ng <- function(p){
 assertive.types::assert_is_any_of(p, 'ggplot')
 p %>%
   ggplot2::ggplot_build() %>%
   magrittr::extract2('layout') %>% 
   magrittr::extract2('layout') %>%
   magrittr::extract2('ROW') %>%
   unique() %>%
   length()
}