R: Creating new column to represent hi/mid/low bins by mean and standard deviation

Question

I've got a batch of survey data that I'd like to be able to subset on a few specific columns which have 0-10 scale data (e.g. Rank your attitude towards x as 0 to 10) so that I can plot using using ggplot() + facet_grid. Faceting will be using 3 hi/med/low bins calculated as +1 / -1 standard deviation above the mean. I have working code, which splits the overall dataframe into 3 parts like so:

# Generate sample data:
structure(list(Q4 = c(2, 3, 3, 5, 4, 3), Q5 = c(1, 3, 3, 3, 2, 
2), Q6 = c(4, 3, 3, 3, 4, 4), Q7 = c(4, 2, 3, 5, 5, 5), Q53_1 = c(5, 
8, 4, 5, 4, 5)), row.names = c(NA, -6L), class = c("tbl_df", 
"tbl", "data.frame"))

# Aquire Q53_1 data as factors
political_scale <- factor(climate_experience_data$Q53_1, levels = c(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10))
# Generate thresholds based on mean and standard deviation thresholds
low_threshold <- round(mean(as.numeric(political_scale, na.rm = T)) - sd(as.numeric(political_scale)), digits = 0)
high_threshold <- round(mean(as.numeric(political_scale, na.rm = T)) + sd(as.numeric(political_scale)), digits = 0)
# Generate low/med/high bins based on Mean and SD
political_lr_low <- filter(climate_experience_data, Q53_1 <= low_threshold)
political_lr_mid <- filter(climate_experience_data, Q53_1 < high_threshold & Q53_1 > low_threshold)
political_lr_high <- filter(climate_experience_data, Q53_1 >= high_threshold)

What I've realised is that this approach really doesn't lend itself to faceting. What I suspect is that I need to use a combination of mutate() across() where() and group_by() to add data to a new column Q53_scale with "hi" "med" "low" based on where Q53_1 values fall in relation to those low/high thresholds (e.g. SD +1 over mean and -1 under mean). My first few dozen attempts have fallen short - has anyone managed to use sd() to bin data for faceting in this way?

Answer 1

library(tidyverse)

climate_experience_data <- structure(list(Q4 = c(2, 3, 3, 5, 4, 3), Q5 = c(
  1, 3, 3, 3, 2,
  2
), Q6 = c(4, 3, 3, 3, 4, 4), Q7 = c(4, 2, 3, 5, 5, 5), Q53_1 = c(
  5,
  8, 4, 5, 4, 5
)), row.names = c(NA, -6L), class = c(
  "tbl_df",
  "tbl", "data.frame"
))

climate_experience_data %>%
  mutate(
    bin = case_when(
      Q53_1 > mean(Q53_1) + sd(Q53_1) ~ "high",
      Q53_1 < mean(Q53_1) - sd(Q53_1) ~ "low",
      TRUE ~ "medium"
    ) %>% factor(levels = c("low", "medium", "high"))
  ) %>%
  
  ggplot(aes(Q4, Q5)) +
    geom_point() +
    facet_grid(~bin)

^{Created on 2022-03-10 by the reprex package (v2.0.0)}