CODEWITHSUNDEEP
rggplot2geom-bar
dan
dan

Reputation: 6314

Color horizontal bars in ggplot's geom_bar

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:

enter image description here

The problems are:

  1. The bar colors in the plot do not match df$col. For example, bars a and b are colored #EBCCD6 rather than #E09898.

  2. 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.

Upvotes: 0

Views: 1594

Answers (1)

shrgm
shrgm

Reputation: 1344

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

enter image description here

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()

enter image description here

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"))

enter image description here

Upvotes: 2

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