Ggplot with facet_wrap and fill in R

Question

I have a dataset of products per specialty and per contract type.

I would like to draw up the number of products per specialty and per contract type. I would like to see individual graphs per specialty (using facet_wrap) and individual bars (with different colors) for each contract.

This is what I have so far, but the "by contract" part doesn't work. What am I doing wrong?

spec <- c(rep(1, 5), rep(2,5), rep(3,5))
prod <- c(rep(15, 3), rep(22, 5), rep(35,2), rep(44, 5))
contract <- sample(c(0,1), replace=TRUE, size=15)

dat <- data.frame(spec=spec, prod=prod, contract = contract)

library(ggplot2)
ggplot(dat, aes(prod), fill=contract) +
  geom_bar(position="dodge")+
  facet_wrap(~spec, scales="free")

Answer 1

First of all, you should convert your input values into factors, as these are discrete values. This can be obtained with factor() .

In the ggplot() function, you have to use aes(x = contract) if you want to have bars for each contract and fill = prod within the aes() for grouping by product.

If I understand your specification correct, this code should give you the desired solution:

library(ggplot2)

spec <- c(rep(1, 5), rep(2,5), rep(3,5))
prod <- c(rep(15, 3), rep(22, 5), rep(35,2), rep(44, 5))
contract <- sample(c(0,1), replace=TRUE, size=15)

dat <- data.frame(spec=factor(spec), 
                      prod=factor(prod), 
                      contract = factor(contract))


ggplot(dat) +
  geom_bar(aes(contract, fill=prod), position = "dodge")+
  facet_wrap(~spec, scales="free")