Creating a density histogram in ggplot2?

Question

I want to create the next histogram density plot with ggplot2. In the "normal" way (base packages) is really easy:

set.seed(46) vector <- rnorm(500)   breaks <- quantile(vector,seq(0,1,by=0.1)) labels = 1:(length(breaks)-1) den = density(vector) hist(df$vector,      breaks=breaks,      col=rainbow(length(breaks)),      probability=TRUE) lines(den) 

With ggplot I have reached this so far:

seg <- cut(vector,breaks,            labels=labels,            include.lowest = TRUE, right = TRUE) df = data.frame(vector=vector,seg=seg)  ggplot(df) +       geom_histogram(breaks=breaks,                     aes(x=vector,                         y=..density..,                         fill=seg)) +       geom_density(aes(x=vector,                       y=..density..)) 

But the "y" scale has the wrong dimension. I have noted that the next run gets the "y" scale right.

 ggplot(df) +       geom_histogram(breaks=breaks,                     aes(x=vector,                     y=..density..,                     fill=seg)) +       geom_density(aes(x=vector,                       y=..density..)) 

I just do not understand it. y=..density.. is there, that should be the height. So why on earth my scale gets modified when I try to fill it?

I do need the colours. I just want a histogram where the breaks and the colours of each block are directionally set according to the default ggplot fill colours.

Answer 1

Manually, I added colors to your percentile bars. See if this works for you.

library(ggplot2)  ggplot(df, aes(x=vector)) +       geom_histogram(breaks=breaks,aes(y=..density..),colour="black",fill=c("red","orange","yellow","lightgreen","green","darkgreen","blue","darkblue","purple","pink")) +     geom_density(aes(y=..density..)) +    scale_x_continuous(breaks=c(-3,-2,-1,0,1,2,3)) +    ylab("Density") + xlab("df$vector") + ggtitle("Histogram of df$vector") +    theme_bw() + theme(plot.title=element_text(size=20),                       axis.title.y=element_text(size = 16, vjust=+0.2),                       axis.title.x=element_text(size = 16, vjust=-0.2),                       axis.text.y=element_text(size = 14),                       axis.text.x=element_text(size = 14),                       panel.grid.major = element_blank(),                       panel.grid.minor = element_blank()) 

Answer 2

fill=seg results in grouping. You are actually getting a different histogram for each value of seg. If you don't need the colours, you could use this:

ggplot(df) +    geom_histogram(breaks=breaks,aes(x=vector,y=..density..), position="identity") +    geom_density(aes(x=vector,y=..density..)) 

If you need the colours, it might be easiest to calculate the density values outside of ggplot2.