How to change bars colors with scale_fill_manual() in R?

January 28, 2023

I want my bars to correspond to a legend and to have them colored with my own color, not the default one.

# library
library(ggplot2)

# create a dataset
specie <- c(rep("IFNg_WNH", 2) , 
            rep("IFNg_AA", 2), 
            rep("IL1b_WNH", 2), 
            rep("IL1b_AA", 2),
            rep("IL6_WNH", 2), 
            rep("IL6_AA", 2) 
)


condition <- rep(c("down", "up"), 6)

value <- c(452,216,
           348,327,
           207,61,
           75,53,
           177,191,
           379,318)
data <- data.frame(specie,condition,value)

data

# Grouped
p <- ggplot(data, aes(fill=condition, y=value, x=specie)) +
  geom_bar(position="dodge", stat="identity")


z <- p+labs(y = "Number of genes", x = "Cytokines")+
  theme_classic()+
  theme(plot.title = element_text(hjust = 0.5))+
  theme(axis.line=element_line(size=1))+
  scale_y_continuous(expand = c(0, 0), limits = c(0, NA))+
  scale_fill_discrete(labels=c('up', 'down'))

z

Once I add

z + scale_fill_manual(values=c('#eb4034','#0a0a0a'))

The color is changing but the legend reverts to the wrong one. What is happening?

>Solution :

Adding type to scale_fill_discrete

type: One of the following:

• A character vector of color codes.

• A list of character vectors of color codes.

• A function that returns a discrete colour/fill scale

ggplot(data, aes(fill=condition, y=value, x=specie)) + 
  geom_bar(position="dodge", stat="identity") + 
  labs(y = "Number of genes", x = "Cytokines") + 
  theme_classic() + 
  theme(plot.title = element_text(hjust = 0.5)) + 
  scale_y_continuous(expand = c(0, 0), limits = c(0, NA)) + 
  scale_fill_discrete(labels=c('up', 'down'), type=c('#eb4034','#0a0a0a'))