Change the fill color of one of the dodged bar in ggplot

Question

I want to change the order of the bar plot only for the last set, just to highlight it. I used scale_fill_manual(), but it didn't help much.

Here's my code:

 x<-c(rep(c("Type1", "Type2"),4))
     y<-c(4,5,6,7,3,4,5,2)
     time<-c(2010,2010,2011,2011,2012,2012,2013,2013)
     z<-data.frame(type = x, val=y, Time = time)

     ggplot(data = z, aes(x=Time,y=val)) +
       geom_bar(stat = "identity", position = "dodge", aes(fill=type))+
       scale_fill_manual(values = c(rep(c("white", "gray51"),3),"white","red"))

Here's the output:

I want the graph to look like:

Is there any way I can do this? I would appreciate any help. I looked at change color of only one bar in ggplot but it doesn't seem to be about grouped data.

Answer 1

My general mantra is that ggplot is very good at plotting the data you give it. If you want it to plot something different, the easiest way is usually to modify your data.

z$type2 = as.character(z$type)
z$type2[z$type == "Type2" & z$Time == 2013] = "Type2 "

I added a sneaky extra space in "Type2 " for the row you want to highlight. It will be a distinct factor level and get its own color (and even be coerced into the a nice order using the alphabetical default). But it will appear the same in the legend label.

ggplot(data = z, aes(x=Time,y=val)) +
    geom_bar(stat = "identity", position = "dodge", aes(fill=type2))+
    scale_fill_manual(values = c("white", "gray50", "red"))

I thought that omitting the red from the legend would be difficult, but this answer showed me that all that is needed is to add breaks = c("Type1", "Type2") as an argument to scale_fill_manual.

Answer 2

What about highlighting the bar with a border. For example:

z$hi = with(z, ifelse(type=="Type2" & Time==2013, "Y","N"))

ggplot(data = z, aes(x=Time,y=val)) +
  geom_bar(stat = "identity", position = "dodge", 
           aes(fill=type, colour=hi), size=1) +
  scale_fill_manual(values=c("gray51","white")) +
  scale_colour_manual(values=c(NA,"red")) +
  guides(colour=FALSE)

UPDATE: In response to your comment: I think a line plot makes it easier to see the trends and the relationships between each type. For example:

ggplot(data = z, aes(x=Time,y=val,colour=type)) +
  geom_line() +
  geom_point() +
  geom_point(data=z[z$hi=="Y",], aes(x=Time, y=val), size=4, pch=1, 
             colour=hcl(195,100,40), stroke=1) +
  scale_y_continuous(limits=c(0,max(z$val))) +
  theme_bw()

Answer 3

Easy to do it with the legend, though you may want to be cautious about throwing users off with the abrupt change in color. Simply add an additional category to your x variable to indicate where you want the highlighting.

x<- xHigh <- c(rep(c("Type1", "Type2"),4))
xHigh[length(xHigh)] <- "Type2_highlight"

myHighlight <- rep("No",length(x))
myHighlight[length(myHighlight)] <- "Yes"
y<-c(4,5,6,7,3,4,5,2)
time<-c(2010,2010,2011,2011,2012,2012,2013,2013)
z<-data.frame(type = x, xHigh = xHigh, val=y, Time = time, myHighlight = myHighlight)

ggplot(data = z, aes(x=Time,y=val)) +
  geom_bar(stat = "identity", position = "dodge", aes(fill=xHigh))+
  scale_fill_manual(values = c(Type1 = "white", Type2 = "gray51", Type2_highlight = "red"))

Another potential option for highlighting a particular bar is to draw a box around it, like so:

ggplot(data = z, aes(x=Time,y=val)) +
  geom_bar(stat = "identity", position = "dodge", aes(fill=type))+
  scale_fill_manual(values = c(Type1 = "white", Type2 = "gray51")) +
  geom_bar(aes(linetype = xHigh)
           , fill = NA
           , stat = "identity", position = "dodge"
           , col = "red"
           , show.legend = FALSE) +
  scale_linetype_manual(values = c(Type1 = 0
                                   , Type2 = 0
                                   , Type2_highlight = 1))

Hope that helps.