ggplot histogram colour by group not working

Question

Ok I have a df like this

a <- c(1,2,2,3)
b <- c(4,5,6,7)
ab <- data.frame(a, b)
ab 

I plot a simple histogram with ggplot and try colour by x variable.

ggplot(ab, aes(x=a, fill=a)) +geom_histogram()

The output plot does not colour. Im clearly making a small error somewhere.

Answer 1

Another way of doing it, a need to be factor

    library(ggplot2)
    a <- c(1,2,2,3)
    b <- c(4,5,6,7)
    ab <- data.frame(a, b)
    ab 
    
    ggplot(ab, aes(x=a, fill=as.factor(a))) +
  geom_histogram()