Add gradient color within groups in ggplot2

Question

I need help in order to add colors to ggplot objects (specificaly geom_bar).

Here is my data

Names       Family          Groups    Values
H.sapiens   A               G1        2
H.erectus   A               G1        6 
H.erectus   B               G2        12
M.griseus   C               G2        3
A.mellifera D               G3        3
L.niger     D               G3        8
H.erectus   D               G3        2
L.niger     A               G1        3
L.niger     B               G2        3
A.mellifera A               G1        8

And so far I suceeded to create this plot :

with this code :

library(ggplot2)
library(ggstance)
library(ggthemes)
ggplot(table, aes(fill=Family, y=Names, x=Values)) + 
  geom_barh(stat="identity",colour="white")+ theme_minimal() +
  scale_x_continuous(limits = c(0,60), expand = c(0, 0))

and now I would like to change the color depending of Groups. More precisely I would like to choose a major color for each group, for instance: G1= blue ; G2 = Green ; G3= Red.

and for each Family to get a gradient within these colors. For instance, B will be darkblue and C ligthblue.

Does someone have an idea, please ?

Here are the data :

dput(table)
structure(list(Names = structure(c(3L, 2L, 2L, 5L, 1L, 4L, 2L, 
4L, 4L, 1L), .Label = c("A.mellifera", "H.erectus", "H.sapiens", 
"L.niger", "M.griseus"), class = "factor"), Family = structure(c(1L, 
1L, 2L, 3L, 4L, 4L, 4L, 1L, 2L, 1L), .Label = c("A", "B", "C", 
"D"), class = "factor"), Groups = structure(c(1L, 1L, 2L, 2L, 
3L, 3L, 3L, 1L, 2L, 1L), .Label = c("G1", "G2", "G3"), class = "factor"), 
    Values = c(2L, 6L, 12L, 3L, 3L, 8L, 2L, 3L, 3L, 8L)), class = "data.frame", row.names = c(NA, 
-10L))

Using multiple color scales in one chart, must be possible through some workaround only. see [this](https://stackoverflow.com/questions/18347147/using-two-scale-colour-gradients-ggplot2) — AnilGoyal, Jun 11 '21 at 10:00

AnilGoyal · Answer 1 · 2021-06-12T11:03:36.027

You may perhaps tweak this one to suit your requirements (I have changed your sample data a bit to show you different gradient among same Group)

df <- read.table(header = T, text = "Names       Family          Groups    Values
H.sapiens   A               G1        2
H.erectus   B               G1        6 
H.erectus   B               G2        12
M.griseus   C               G2        3
A.mellifera D               G3        3
L.niger     D               G3        8
H.erectus   A               G3        2
L.niger     A               G1        3
L.niger     B               G2        3
A.mellifera C               G1        8")

library(tidyverse)
df %>% ggplot() +
  geom_col(aes(x = Names, y = Values, fill = Groups, alpha = as.integer(as.factor(Family)))) +
  coord_flip() +
  scale_fill_manual(name = "Groups", values = c("blue", "green", 'red')) +
  scale_alpha_continuous(name = "Family", range = c(0.2, 0.7)) +
  theme_classic()

^{Created on 2021-06-12 by the reprex package (v2.0.0)}

This solution is so much cleaner, good idea to use alpha. I'd suggest to remove the background grey. — zx8754, Jun 11 '21 at 11:47
@zx8754 thanks. The idea was to show the lead only. In fact there is so much other things to be taken care of like labels, etc. not only legend — AnilGoyal, Jun 11 '21 at 11:54

score 1 · Accepted Answer · answered Jun 11 '21 at 09:47

We can create range of colours for each Group then match on order of Family. You might need to play around with colours to make the difference more prominent:

cols <- lapply(list(G1 = c("darkblue", "lightblue"),
                    G2 = c("darkgreen", "lightgreen"),
                    G3 = c("red4", "red")),
               function(i) colorRampPalette(i)(length(unique(table$Family))))

table$col <- mapply(function(g, i) cols[[ g ]][ i ], 
                    g = table$Groups, i = as.numeric(table$Family))

ggplot(table, aes(x = Values, y = Names, fill = col )) + 
  geom_barh(stat = "identity", colour = "white") +
  scale_x_continuous(limits = c(0, 60), expand = c(0, 0)) +
  scale_fill_identity() +
  theme_minimal()

Thanks a lot, and how can I add the legend of the gradient color ? — chippycentra, Jun 11 '21 at 10:51
@chippycentra see this post: https://stackoverflow.com/a/18395012/680068 — zx8754, Jun 11 '21 at 11:53

Add gradient color within groups in ggplot2

2 Answers2