Histogramns of the data grouped by month

Question

If I would like to aggregate the data by month, an approach is the following:

library(dplyr)
library(lubridate)
set.seed(2017)
options(digits=4)

(expenses <- data_frame(
   date=seq(as.Date("2016-01-01"), as.Date("2016-12-31"), by=1),
   amount=rgamma(length(date), shape = 2, scale = 20)))

Then I summarized them by month like this:

expenses %>% group_by(month=floor_date(date, "month")) %>%
summarize(amount=sum(amount))

I would like to plot an histogram of the variable amount for each month. How could I do it?

Answer 1

Extract the month value from date and using facets you can show histogram for every month in separate plots.

library(dplyr)
library(ggplot2)

expenses %>%
  arrange(date) %>%
  mutate(month = format(date, '%b %Y'), 
         month = factor(month, unique(month))) %>%
  ggplot() + aes(amount) + 
  geom_histogram(bins = 10) + 
  facet_wrap(~month)