how to plot a raster file as a histogram using ggplot2?

Question

I have a raster file and I want to plot as a histogram ,i did it using hist() as shown below. but i would like to plot using ggplot2 which plot it in a better way for publication.

conne <- file("C:\\fined.bin","rb")
r = raster(y)
hist(r, breaks=30, main="SMD_2010",
        xlab="Pearson correlation", ylab="Frequency", xlim=c(-1,1))

I tried this:

  qplot(rating, data=r, geom="histogram")

Error:

            ggplot2 doesn't know how to deal with data of class RasterLayer

I need to plot something like:

http://docs.ggplot2.org/0.9.3/geom_histogram-28.png

Answer 1

As a fast solution You can use the result of hist

f <- hist(r, breaks=30)
dat <- data.frame(counts= f$counts,breaks = f$mids)
ggplot(dat, aes(x = breaks, y = counts)) + 
  geom_bar(stat = "identity",fill='blue',alpha = 0.8)+
  xlab("Pearson correlation")+ ylab("Frequency")+
  scale_x_continuous(breaks = seq(-1,1,0.25),  ## without this you will get the same scale
                   labels = seq(-1,1,0.25))    ## as hist (question picture)

PS : Maybe you need to use scale_x_discrete to get better axis look

EDIT to add gradient fill

ggplot(dat, aes(x = breaks, y = counts, fill =counts)) + ## Note the new aes fill here
  geom_bar(stat = "identity",alpha = 0.8)+
  xlab("Pearson correlation")+ ylab("Frequency")+
  scale_x_continuous(breaks = seq(-1,1,0.25),
                   labels = seq(-1,1,0.25))+
  scale_fill_gradient(low="blue", high="red")            ## to play with colors limits