R packages used in this section
library(DT)
library(gapminder)
library(gghighlight)
library(ggrepel)
library(stargazer)
library(tidyverse)
1. Histogram
- A histogram is an approximate representation of the distribution of
numerical data.
Diffenece between a barchart and a histogram
| Discrete variable |
Bar chart |
Lines between bars |
| Continuous variable |
Histogram |
No Lines between bars |
|
|
|
When x-axis is year of elections
- There is no values between 2017 and 2021 (because there was no
election held between them)
- Years of election look like numeric, but it is not treated as
numeric
When x-axis is vote share
- The value of vote share ranges from 0%, 0.1%, …. to 100%
→ We need infinite number of bars for each value
→ We do not use bars for each value
- We use limited number of bars
2. How to draw a histogram using ggplot2
- You can draw a histogram by using
geom_histogram()
- You need to map a continuous variable on
x-axis
- You don’t have to map on
y-axis
- Let’s draw a histogram of vote share in the lower house elections in
Japan between 1996 and 2021
2.1 Draw a simple histogram
- Make a folder, named
data in your R Project folder
- Download hr96-21.csv onto the
data folder in your R Project
- Read the election data,
hr96-21.csv and name it
df
df <- read_csv("data/hr96-21.csv",
na = ".")
- Using
if_else(), make a dummy variable:
ldp
#####
mutate(ldp = if_else(seito == "自民", "LDP", "Non-LDP") -
This command means make a dummy variable, named ldp
- If a value in variable
seito is “自民”, then replace it
with “LDP” and replace the other values (that is, the other party names)
in seito with “Non-LDP”
df <- df %>%
mutate(ldp = if_else(seito == "自民", "LDP", "Non-LDP"))
- Draw a histogram of vote share
df %>%
ggplot() +
geom_histogram(aes(x = voteshare))
