scale_fill_viridis_c color bar on a log scale

Question

I hope this is not a duplicate but I can't scour the internet much longer. I really would like to generate a heatmap but have the colorbar be on a log scale. I don't necessarily want to convert my values to log, but rather alter the color bar so it runs from 0, 0.01, 0.1, 1, 10, 100. I included a reprex that shows an example of the data I'm working with, and below that is a figure from a paper that I'm hoping to recapitulate.

library(tidyverse)

my_data <- tibble(sample_name = rep(c("A", "B", "C"), 3),
                  sample_genus = c(rep("Genus1", 3), rep("Genus2", 3),rep("Genus3", 3)),
                  sample_abundance = c(0,5,45,0.3,0.01,15,1,8,89))

ggplot(data = my_data, aes(x = sample_name,
                           y = sample_genus,
                           fill = sample_abundance)) +
  geom_tile() +
  scale_fill_viridis_c(limits = c(0, 100))

^{Created on 2019-08-16 by the reprex package (v0.3.0)}

https://stackoverflow.com/questions/8069837/is-there-a-built-in-way-to-do-a-logarithmic-color-scale-in-ggplot2 — Jon Spring, Aug 16 '19 at 20:39

score 13 · Accepted Answer · answered Aug 16 '19 at 21:07

Here's an approach using scales::pseudo_log_trans, which lets us plot 0 but transition to a log scaling beyond 1.

my_breaks <- c(0, 0.01, 0.1, 1, 10, 100)

ggplot(data = my_data, aes(x = sample_name,
                           y = sample_genus,
                           fill = sample_abundance)) +
  geom_tile() +
  scale_fill_viridis_c(breaks = my_breaks, labels = my_breaks, 
                       trans = scales::pseudo_log_trans(sigma = 0.001))

scale_fill_viridis_c color bar on a log scale

1 Answers1