CODEWITHSUNDEEP
rggplot2geom-bar
James
James

Reputation: 729

ggplot geom_bar continuous colour fill with a separate color based on a conditional

Here is a reproducible sample data set that has a continuous fill based on Amount. As you can see from the sample below, I also have a column in d called flag. What I want is to be able to visualize flag by changing the border color of the bar to the color red.

# create reproducible data
library(ggplot2)
d <- read.csv(text='Day,Location,Length,Amount,flag
    1,4,3,1.1,FALSE
    1,3,1,2,FALSE
    1,2,3,4,FALSE
    1,1,3,5,FALSE
    2,0,0,0,FALSE
    3,3,3,1.8,TRUE
    3,2,1,3.54,FALSE
    3,1,3,1.1,FALSE',header=T)
ggplot(d, aes(x = Day, y = Length)) + 
geom_bar(aes(fill = Amount, order = -Location), stat = "identity")

I have experimented with alpha and that certainly does flag the desired bar but fails to visualize the data in the way I want:

ggplot(d, aes(x = Day, y = Length)) + 
geom_bar(aes(fill = Amount, order = -Location, alpha = -flag), stat = "identity")

alpha when using -flags (note -)also messes with the legend, which is undesirable.

Using the below command returns an error that I need 2 colour variables, but I only want 1, red:

ggplot(d, aes(x = Day, y = Length)) + 
geom_bar(aes(fill = Amount, order = -Location, alpha = -flag), stat = "identity") + 
scale_colour_manual(values = alpha(c('red')))

To recap:

  1. I want to show the bar where flag = TRUE with a red outline (or something equally as noticeable) without changing the continuous scale already decided by Amount.

  2. I want the legend to reflect that flag = TRUE with the colour red (or whatever matches).

I was not able to find an applicable solution perusing the web so any thoughts or suggestions are much appreciated!

Upvotes: 1

Views: 2389

Answers (1)

mathematical.coffee
mathematical.coffee

Reputation: 56905

Use colour=flag (colour is the outline in a geom_bar while fill is the fill). Then add + scale_colour_manual(values=c(NA, 'red')) where NA is used if flag is false (no border) and 'red' is used if flag is true.

ggplot(d, aes(x = Day, y = Length)) + 
geom_bar(aes(fill = Amount, order = -Location, col=flag), stat = "identity") +
  scale_colour_manual(values=c(NA, 'red'))

(Note: instead you could geom_bar(aes(...), col=ifelse(d$flag, 'red', NA)) and skip the scale_colour_manual but then you don't get a legend).

enter image description here

If you want to increase the border width, add a lwd=<new line width> in your geom_bar (outside the aes).

Upvotes: 3

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