Weird behavior of ggplot combined with fill and scale_y_log10()

Question

I'm trying to produce a histogram with ggplot's geom_histogram which colors the bars according to a gradient, and log10's them.

Here's the code:

library(ggplot2)

set.seed(1)
df <- data.frame(id=paste("ID",1:1000,sep="."),val=rnorm(1000),stringsAsFactors=F)

bins <- 10
cols <- c("darkblue","darkred")
colGradient <- colorRampPalette(cols)
cut.cols <- colGradient(bins)
df$cut <- cut(df$val,bins)
df$cut <- factor(df$cut,level=unique(df$cut))

Then,

ggplot(data=df,aes_string(x="val",y="..count..+1",fill="cut"))+
  geom_histogram(show.legend=FALSE)+
  scale_color_manual(values=cut.cols,labels=levels(df$cut))+
  scale_fill_manual(values=cut.cols,labels=levels(df$cut))+
  scale_y_log10()

gives:

whereas dropping the fill from the aesthetics:

ggplot(data=df,aes_string(x="val",y="..count..+1"))+
  geom_histogram(show.legend=FALSE)+
  scale_color_manual(values=cut.cols,labels=levels(cuts))+
  scale_fill_manual(values=cut.cols,labels=levels(cuts))+
  scale_y_log10()

gives:

Any idea why do the histogram bars differ between the two plots and to make the first one similar to the second one?

By default, `geom_histogram` uses `position_stack`. You can change that to `position_identity`, but then you might want to make the bars transparent. I recommend using faceting instead. — Roland, Jun 16 '17 at 06:34

Uwe · Answer 1 · 2017-06-16T22:13:43.097

The OP is trying to produce a histogram with ggplot's geom_histogram which colors the bars according to a gradient...

The OP has already done the binning (with 10 bins) but is then calling geom_histogram() which does a binning on its own using 30 bins by default (see ?geomhistogram).

When geom_bar() is used instead together with cutinstead of val

ggplot(data = df, aes_string(x = "cut", y = "..count..+1", fill = "cut")) +
  geom_bar(show.legend = FALSE) +
  scale_color_manual(values = cut.cols, labels = levels(df$cut)) +
  scale_fill_manual(values = cut.cols, labels = levels(df$cut)) +
  scale_y_log10()

the chart becomes:

Using geom_histogram() with filled bars is less straightforward as can be seen in this and this answer to the question How to fill histogram with color gradient?

Weird behavior of ggplot combined with fill and scale_y_log10()

1 Answers1