how to use labeller() functions to get column totals to appear in the label of a facet when using the facet_grid() function in ggplot2

Question

here\'s a data set to give context to my question:

library(tidyr); library(dplyr); library(ggplot2)
set.seed(1)
dfr2 <- tibble(x1 = factor(sample(letters[1         


        

Answer 1

I think the cleanest approach for a situation like yours would be to use a lookup table for your labeller instead of a function:

lookup <- c(
  grp1 = "grp1 (N = 20)",
  grp2 = "grp2 (N = 30)"
)

ggplot(plot_data_prepr(dfr2, "grpA", "x1"), aes(x = x1, y = pct2, fill = x1)) +
  geom_bar(stat = 'identity') +
  ylim(0,1) +
  geom_text(aes(label=pct_lab, y = pct_pos + .02)) +
  facet_grid(. ~ grpA, labeller = labeller(grpA = lookup))

If you think your group totals might change in the future, you can also auto-generate the labels by processing the data beforehand and extracting the necessary parts:

data <- plot_data_prepr(dfr2, "grpA", "x1")

lookup <- c(
    grp1 = paste0("grp1 (N = ", data$grp_tot[data$grpA == "grp1"][1], ")"),
    grp2 = paste0("grp2 (N = ", data$grp_tot[data$grpA == "grp2"][1], ")")
)

ggplot(data, aes(x = x1, y = pct2, fill = x1)) + 
  geom_bar(stat = 'identity') +
  ylim(0,1) +
  geom_text(aes(label=pct_lab, y = pct_pos + .02)) +
  facet_grid(. ~ grpA, labeller = labeller(grpA = lookup)) 

Answer 2

With minimal modification, the following code (only last ggplot)

dd <- plot_data_prepr(dat = dfr2, groupvar = "grpA", mainvar = "x1")

lookup <- unique(dd$grp_tot)

plusN <- function(string) {
  label <- paste0(string, ' (N = ',lookup,')')
  label
}

ggplot(plot_data_prepr(dfr2, "grpA", "x1"),
       aes(x = x1, y = pct2, fill = x1)) +
  geom_bar(stat = 'identity') +
  ylim(0,1) +
  geom_text(aes(label=pct_lab, y = pct_pos + .02)) +
  facet_grid(. ~ grpA, labeller = labeller(grpA = plusN)) 

gives this output:

Please note that this works regardless of the number of groups within grpA.