change color of only one bar in ggplot

Question

I want to color only one bar in ggplot. This is my data frame:

area <- c("Północ", "Południe", "Wschód", "Zachód")
sale <- c(16.5, 13.5, 14, 13)
df.sale <- data.frame(area, sale)
colnames(df.sale) <- c("Obszar sprzedaży", "Liczba sprzedanych produktów (w tys.)")

And code for plotting:

plot.sale.bad <- ggplot(data=df.sale, aes(x=area, y=sale, fill=area)) +
  geom_bar(stat="identity") +
  scale_fill_manual(values=c("black", "red", "black", "black")) +
  xlab(colnames(df.sale)[1]) +
  ylab(colnames(df.sale)[2]) +
  ggtitle("Porównanie sprzedaży") 

I would like to have only one bar colored and 3 others to have default color (darkgrey, not black, it looks bad for me). How can I change color of only on bar or how to get name of the default color of bars to put them instead of black?

Answer 1

Option 1: Change color of only one bar. Following Henrick's suggestion, you can create a new variable with NAs for the default color and character strings/factors for non-default colors (the first one happens to be red):

area.color <- c(NA, "withcolor", NA, NA)
plot.sale.bad <- ggplot(data=df.sale, aes(x=area, y=sale, fill=area.color)) +
  geom_bar(stat="identity") +
  xlab(colnames(df.sale)[1]) +
  ylab(colnames(df.sale)[2]) +
  ggtitle("Porównanie sprzedaży") 
plot.sale.bad

Option 2: Find the name of the default dark gray color you like. This is not the default color if you simply remove the scale_fill_manual line in your original code (in that case, you get four different pastels), so I assume you mean the grey color produced by the code chunk just above this paragraph, for those bars where area.color==NA. In that case, you might look at the source code (or args, anyway) for scale_fill_discrete:

> args(scale_fill_discrete)
# function (..., h = c(0, 360) + 15, c = 100, l = 65, h.start = 0, 
#     direction = 1, na.value = "grey50") 
# NULL

The default for na.value is "grey50". So if you wanted to use scale_fill_manual, you could do it like so:

plot.sale.bad <- ggplot(data=df.sale, aes(x=area, y=sale, fill=area)) +
  geom_bar(stat="identity") +
  scale_fill_manual(values=c("grey50", "red", "grey50", "grey50")) +
  xlab(colnames(df.sale)[1]) +
  ylab(colnames(df.sale)[2]) +
  ggtitle("Porównanie sprzedaży") 
plot.sale.bad