A great ggplot twist

Programming with dplyr

Dr. Chester Ismay

Educator, Data Scientist, and R/Python Consultant

ggplot2 basics

library(ggplot2)
ggplot(
    world_bank_data, 
    aes(x = infant_mortality_rate)
) +

  geom_histogram(color = "white")

Histogram of infant_mortality_rate

Adding a title

ggplot(
    world_bank_data, 
    aes(x = infant_mortality_rate)
) + 
  geom_histogram(color = "white") +

  ggtitle("A histogram of infant_mortality_rate")

ggplot2 with title

Wrapping into a function

# Previous plot code
ggplot(world_bank_data, aes(x = infant_mortality_rate)) + 
  geom_histogram(color = "white") +
  ggtitle("A histogram of infant_mortality_rate")

# Define a function
my_histogram <- function(

    df, x_var) {

  ggplot(df, aes(x = x_var)) +
    geom_histogram(color = "white") +
    ggtitle(paste("A histogram of", x_var))
}

Working on our function

# First attempt at a function
my_histogram <- function(df, x_var) {
  ggplot(df, aes(x = x_var)) +
    geom_histogram(color = "white") +
    ggtitle(paste("A histogram of", x_var))
}

# Call the function
my_histogram(df = world_bank_data, 
             x_var = infant_mortality_rate)

 Error in paste("A histogram of", x_var) : 
  object 'infant_mortality_rate' not found

Adding in rlang

# First attempt at a function
my_histogram <- function(df, x_var) {
  ggplot(df, aes(x = x_var)) +
    geom_histogram(color = "white") +
    ggtitle(paste("A histogram of", x_var))
}

# Making needed tweaks to stop error
my_histogram <- function(df, x_var) {
  ggplot(df, aes(x = {{ x_var }})) +

    geom_histogram(color = "white") +
    ggtitle(paste("A histogram of",

            as_label(enquo(x_var)))
}

Using our function

# Defined function with rlang operators
my_histogram <- function(df, x_var) {
  ggplot(df, aes(x = {{ x_var }})) +
    geom_histogram(color = "white") +
    ggtitle(paste(
      "A histogram of", 
      as_label(enquo(x_var))
    ))
}

# Call the function with the pipe!
world_bank_data %>% 
  my_histogram(x_var = perc_rural_pop)

ggplot2 with rlang histogram

Let's practice!

Programming with dplyr