CODEWITHSUNDEEP
rggplot2geom-bar
Emma Kate Loveday
Emma Kate Loveday

Reputation: 1

How do I change the fill color for a computed variable in geom_bar

I am trying to change the default fill color from blue to green or red. Here is the code I am using

Top_pos<- ggplot(Top_10, aes(x=reorder(Term,Cs), y=Cs, fill=pvalue)) + 
    geom_bar(stat = "identity", colour="black") + coord_flip()

Using the above code, I get the following image. I have no problem with this data but I do not know how to change the fill color.

bar plot with current colors

Upvotes: 0

Views: 1376

Answers (2)

camille
camille

Reputation: 16832

It's easy to confuse scaling the color and scaling the fill. In the case of geom_bar/geom_col, color changes the borders around the bars while fill changes the colors inside the bars.

You already have the code that's necessary to scale fill color by value: aes(fill = pvalue). The part you're missing is a scale_fill_* command. There are several options; some of the more common for continuous scales are scale_fill_gradient or scale_fill_distiller. Some packages also export palettes and scale functions to make it easy to use them, such as the last example which uses a scale from the rcartocolor package.

scale_fill_gradient lets you set endpoints for a gradient; scale_fill_gradient2 and scale_fill_gradientn let you set multiple midpoints for a gradient.

scale_fill_distiller interpolates ColorBrewer palettes, which were designed for discrete data, into a continuous scale.

library(tidyverse)

set.seed(1234)
Top_10 <- tibble(
    Term = letters[1:10],
    Cs = runif(10),
    pvalue = rnorm(10, mean = 0.05, sd = 0.005)
)

plt <- ggplot(Top_10, aes(x = reorder(Term, Cs), y = Cs, fill = pvalue)) +
    geom_col(color = "black") +
    coord_flip()

plt + scale_fill_gradient(low = "white", high = "purple")


plt + scale_fill_distiller(palette = "Greens")


plt + rcartocolor::scale_fill_carto_c(palette = "Sunset")

Created on 2018-05-05 by the reprex package (v0.2.0).

Upvotes: 1

Punintended
Punintended

Reputation: 737

Personally, I'm a fan of R Color Brewer. It's got a set of built-in palettes that play well together for qualitative, sequential or diverging data types. Check out colorbrewer2.org for some examples on real-ish data

More generally, and for how to actually code it, you can always add a scale_fill_manual argument. There are some built-ins in ggplot2 for gradients (examples here)

Upvotes: 0

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