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

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

gg_facet_nrow(p)