How to Create Histogram by Group in R

Prerequisites

• Load the ggplot2 package and set the theme function theme_classic() as the default theme:

library(ggplot2)
theme_set(
  theme_classic() + 
    theme(legend.position = "top")
  )

• Create a demo dataset: Weight data by sex:

set.seed(1234)
wdata = data.frame(
        sex = factor(rep(c("F", "M"), each=200)),
        weight = c(rnorm(200, 55), rnorm(200, 58))
        )

head(wdata, 4)

##   sex weight
## 1   F   53.8
## 2   F   55.3
## 3   F   56.1
## 4   F   52.7

Create histogram by group

# Change line color by sex
ggplot(wdata, aes(x = weight)) +
  geom_histogram(aes(color = sex), fill = "white",
                position = "identity", bins = 30) +
  scale_color_manual(values = c("#00AFBB", "#E7B800")) 


# change fill and outline color manually 
ggplot(wdata, aes(x = weight)) +
  geom_histogram(aes(color = sex, fill = sex), 
                position = "identity", bins = 30, alpha = 0.4) +
  scale_color_manual(values = c("#00AFBB", "#E7B800")) +
  scale_fill_manual(values = c("#00AFBB", "#E7B800"))