How do I use a dynamically declared variable in R ggplot when using count() and factor() functions?

user_14246805 0
Viewed 386

I would like to plot some relative frequency data using ggplot in a more efficient manner.

I have many variables of interest, and want to plot a separate barchart for each. The following is my current code for one variables of interest Gender:

chart.gender <- data %>% 
     count(Gender = factor(Gender)) %>% 
     mutate(Gender = fct_reorder(Gender,desc(n))) %>% 
     mutate(pct = prop.table(n)) %>% 
     ggplot(aes(x=Gender, y=n, fill=Gender)) +
            geom_col()

This works, but the variable Gender is repeated many times. Since I need to repeat plots for many variables of interest (Gender, Age, Location, etc.) with similar code, I would like to simplify this by declaring the variable of interest once at the top and using that declared variable for the rest of the code. Intuitively, something like:

var <- "Gender"
chart.gender <- data %>% 
     count(var = factor(var)) %>% 
     mutate(var = fct_reorder(var,desc(n))) %>% 
     mutate(pct = prop.table(n)) %>% 
     ggplot(aes(x=var, y=n, fill=var)) +
            geom_col()

Which does not result in a plot of three-level factor count of gender frequencies, but merely a single column named 'Gender'. I believe I see why it's not working, but I do not know the solution for it: I want R to retrieve the variable name I stored in var, and then use that to retrieve the data for that variable in 'data'.

With some research I've found suggestions like using as.name(var), but there seems to (at the least) be a problem with declaring the variable var as a factor within the count() function.

Some reproducible data:

library(tidyverse)
library(ggplot2)

set.seed(1)
data <- data.frame(sample(c("Male", "Female", "Prefer not to say"),20,replace=TRUE))
colnames(data) <- c("Gender")

I'm using the following packages in R: tidyverse, ggplot2

dplyr r
2 Answers

Use .data pronound to subset the column with var as variable.

library(tidyverse)

var <- "Gender"
data %>% 
  count(var = factor(.data[[var]])) %>% 
  mutate(var = fct_reorder(var,desc(n))) %>% 
  mutate(pct = prop.table(n)) %>% 
  ggplot(aes(x=var, y=n, fill=var)) +
  geom_col()

Or another way would be using sym and !!

data %>% 
  count(var = factor(!!sym(var))) %>% 
  mutate(var = fct_reorder(var,desc(n))) %>% 
  mutate(pct = prop.table(n)) %>% 
  ggplot(aes(x=var, y=n, fill=var)) +
  geom_col()
user_39629140

If you use as.name() when you set the variable initially, you can use !! ("bang-bang") to unquote the variable for the count() step.

var <- as.name("Gender")

chart.gender <- data %>% 
     count(var = factor(!! var)) %>% 
     mutate(var = fct_reorder(var,desc(n))) %>% 
     mutate(pct = prop.table(n)) %>% 
     ggplot(aes(x=var, y=n, fill=var)) +
     geom_col()
user_119638300
Related