Fill boxplot by variable but keep date scale GGplot-CodePudding

I have a dataframe containing values for three variables at three different dates:

df <- data.frame(date = as.Date(c(rep('2021-01-01',6),rep('2021-05-04',6),rep('2015-04-04',6))),
             variable = rep(c('apple','bananna','carrot'),6),
             value = rnorm(18,5,2))

I'd like to make a boxplot with fill relating to variable, date on the x axis and value on the y axis:

ggplot(df,aes(x=as.factor(date),y=value,fill=variable)) geom_boxplot()

This fills based on variable, but it doesn't scale date according to the actual differences in time:

If I set group=date, it gets scaled properly, but fill=variable stops working:

ggplot(df,aes(x=date,y=value,group=date,fill=variable)) geom_boxplot()

How do I get the date to scale properly and also fill based on variable name?

CodePudding user response：

Seems like this was already answered

CodePudding user response：

The problem can be solved with the creation of a factor variable combining date and variable. This is done with interaction.

I have also added code to increase the plot window width, in order to make the bars and labels more visible.

df <- data.frame(date = as.Date(c(rep('2021-01-01',6),rep('2021-05-04',6),rep('2015-04-04',6))),
                 variable = rep(c('apple','bananna','carrot'),6),
                 value = rnorm(18,5,2))

library(ggplot2)

x11(width = 20, height = 8)    # this is not stricktly needed

ggplot(df, aes(x = date, y = value, fill = variable))  
  geom_boxplot(aes(group = interaction(date, variable)))  
  scale_x_date(
    breaks = unique(df$date),
    date_labels = "%Y-%m-%d"
  )  
  theme(axis.text.x = element_text(angle = 45, vjust = 1, hjust = 1))

^{Created on 2022-06-02 by the reprex package (v2.0.1)}

The same can be done by creating a temporary new factor in a dplyr pipe to mutate.

suppressPackageStartupMessages({
  library(ggplot2)
  library(dplyr)
})

df %>%
  mutate(group = interaction(date, variable)) %>%
  ggplot(aes(x = date, y = value, fill = variable))  
  geom_boxplot(aes(group = group))  
  scale_x_date(
    breaks = unique(df$date),
    date_labels = "%Y-%m-%d"
  )  
  theme(axis.text.x = element_text(angle = 45, vjust = 1, hjust = 1))

^{Created on 2022-06-02 by the reprex package (v2.0.1)}