Color horizontal bars in ggplot's geom_bar

Question

I'm having some trouble with ggplot2's geom_bar:

Here's my data:

set.seed(1)
df <- data.frame(log10.p.value = -10*log10(runif(10,0,1)), y = letters[1:10], col = rep("#E0E0FF",10), stringsAsFactors = F)
#specify color by log10.p.value
df$col[which(df$log10.p.value > 2)] <- "#EBCCD6"
df$col[which(df$log10.p.value > 4)] <- "#E09898"
df$col[which(df$log10.p.value > 6)] <- "#C74747"
df$col[which(df$log10.p.value > 8)] <- "#B20000"
#truncate bars
df$log10.p.value[which(df$log10.p.value > 10)] <- 10

As you can see each log10.p.value interval is assigned a different color and since I don't want the bars to extend beyond log10.p.value = 10 I set any such value to 10.

My ggplot command is:

p <- ggplot(df, aes(y=log10.p.value,x=y,fill=as.factor(col)))+
  geom_bar(stat="identity",width=0.2)+coord_flip()+scale_y_continuous(limits=c(0,10),labels=c(seq(0,7.5,2.5)," >10"))+
  theme(axis.text=element_text(size=10))+scale_fill_manual(values=df$col,guide=FALSE)

And the figure is:

The problems are:

The bar colors in the plot do not match df$col. For example, bars a and b are colored #EBCCD6 rather than #E09898.
Because I manually specify the x-axis last tick text to be ">10" an extra space is created in the plot to the right of that tick making the bars I truncated at 10 seem like they end at 10, whereas my intention was for them to go all the way to the right end of the plot.

for me it works , why don't you think that it is not matching ? maybe use windows() X11() for linux and quartz() for mac before plotting so you will have a bigger window ? for limiting the plot in ggplot you should use coord_cartesian as explained here http://stackoverflow.com/questions/25685185/limit-ggplot2-axes-without-removing-data-outside-limits-zoom — , May 21 '16 at 08:08
Updated my answer to include the correct way of specifying colours through scale_colour_manual. However, your graph is not reproducible, so you will still need to check that. — shrgm, May 21 '16 at 10:28

shrgm · Accepted Answer · 2016-05-21T10:26:44.487

I am unable to reproduce the graph that you generated. Running the code you've provided generates the following graph:

You can correctly specify the colours by naming the vector that you are passing to scale_fill_manual:

coloursv <- df$col
names(coloursv) <- df$col

To the second part of your question - you can make sure there is no space between the bars and the edge of the graph using the expand parameter of scale_y_continuous.

Making these two changes, the code for the plot becomes:

p <- ggplot(df, aes(y=log10.p.value,x=y,fill=as.factor(col)))+
    geom_bar(stat="identity",width=0.2) +
    scale_y_continuous(limits=c(0,10),
                       labels=c(seq(0,7.5,2.5)," >10"),
                       expand = c(0,0)) +
    theme(axis.text=element_text(size=10)) +
    scale_fill_manual(values = coloursv,guide = F) +
    coord_flip()

The '>10' label is a bit cut-off. You can increase the plot margins to make it visible, using:

p + theme(plot.margin=unit(c(0.1,0.5,0.1,0.1),"cm"))

Color horizontal bars in ggplot's geom_bar

1 Answers1