How to control ordering of stacked bar chart using identity on ggplot2

Question

Using this dummy data.frame

ts <- data.frame(x=1:3, y=c("blue", "white", "white"), z=c("one", "one", "two"))

I try and plot with category "blue" on top.

ggplot(ts, aes(z, x, fill=factor(y, levels=c("blue","white" )))) + geom_bar(stat = "identity")

gives me "white" on top. and

ggplot(ts, aes(z, x, fill=factor(y, levels=c("white", "blue")))) + geom_bar(stat = "identity")

reverses the colors, but still gives me "white" on top. How can I get "blue" on top?

Edible

Answer 1

I've struggled with the same issue before. It appears that ggplot stacks the bars based on their appearance in the dataframe. So the solution to your problem is to sort your data by the fill factor in the reverse order you want it to appear in the legend: bottom item on top of the dataframe, and top item on bottom:

ggplot(ts[order(ts$y, decreasing = T),],
       aes(z, x, fill=factor(y, levels=c("blue","white" )))) + 
  geom_bar(stat = "identity")

Edit: More illustration

Using sample data, I created three plots with different orderings of the dataframe, I thought that more fill-variables would make things a bit clearer.

set.seed(123)
library(gridExtra)
df <- data.frame(x=rep(c(1,2),each=5),
                 fill_var=rep(LETTERS[1:5], 2),
                 y=1)
#original order   
p1 <- ggplot(df, aes(x=x,y=y,fill=fill_var))+
  geom_bar(stat="identity") + labs(title="Original dataframe")


#random order
p2 <- ggplot(df[sample(1:10),],aes(x=x,y=y,fill=fill_var))+
  geom_bar(stat="identity") + labs(title="Random order")
#legend checks out, sequence wird

#reverse order
p3 <- ggplot(df[order(df$fill_var,decreasing=T),],
             aes(x=x,y=y,fill=fill_var))+
  geom_bar(stat="identity") + labs(title="Reverse sort by fill")

plots <- list(p1,p2,p3)

do.call(grid.arrange,plots)

Jonathonjonati

Thank you for the thorough example! I thought the order was determined alphabetically, so this is very helpful. – Edible

You're welcome! If any of the provided solutions work to your satisfaction, can you accept one? Keeps others from answering the question. – Jonathonjonati

Nice answer! Perhaps others will find this SO question useful: #30740102 – Schnapp

Unfortunately this doesn't seem to work with dplyr's arrange() function. Switching the order of the stack category has no effect. – Unalterable

All of the plots in your example have the same order for me (R 3.4.3) – Onslaught

It's quite an old answer. Maybe have a look at Inhabitant's solution below. – Jonathonjonati

Answer 2

For what it is worth, in ggplot2 version 2.2.1 the order of the stack is no longer determined by the row order in the data.frame. Instead, it matches the order of the legend as determined by the order of levels in the factor.

d <- data.frame(
  y=c(0.1, 0.2, 0.7),
  cat = factor(c('No', 'Yes', 'NA'), levels = c('NA', 'Yes', 'No')))

# Original order
p1 <- ggplot(d, aes(x=1, y=y, fill=cat)) +
  geom_bar(stat='identity')

# Change order of rows
p2 <- ggplot(d[c(2, 3, 1), ], aes(x=1, y=y, fill=cat)) +
  geom_bar(stat='identity')

# Change order of levels
d$cat2 <- relevel(d$cat, 'Yes')
p3 <- ggplot(d, aes(x=1, y=y, fill=cat2)) +
  geom_bar(stat='identity') 

grid.arrange(p1, p2, p3, ncol=3)

It results in the below plot:

Kinglet

Thank you for telling us it is due to the new ggplot2 version. Somehow my plots were suddenly all wrong and I spent a lot of time locating the mistake with myself. Only now I know the problem is with 'ggplot2' instead and I can safely change the order manually – Jordans

Oh my gosh, I spent like an hour trying to figure out why the behavior of my code had changed... – Flagitious

I was struggling with the ordering of NA values and it needs to be added as a proper level. An easy way to do just that is the convenience function addNA(). – Stuartstub

Ecksters, watch your words – Sarcocarp

Note that if you're using scale_fill_identity(), this means that your bar will stacked in the order of the values that you're using to specify colours - so hexadecimal colour codes will be alphanumerically sorted to determine the order of both the legend and the bar stacking. – Turnbow

Answer 3

Messing with your data in order to make a graph look nice seems like a bad idea. Here's an alternative that works for me when using position_fill():

ggplot(data, aes(x, fill = fill)) + geom_bar(position = position_fill(reverse = TRUE)) 

The reverse = TRUE argument flips the order of the stacked bars. This works in position_stack also.

Ariana

Answer 4

Use the group aethetic in the ggplot() call. This ensures that all layers are stacked in the same way.

series <- data.frame(
  time = c(rep(1, 4),rep(2, 4), rep(3, 4), rep(4, 4)),
  type = rep(c('a', 'b', 'c', 'd'), 4),
  value = rpois(16, 10)
)

ggplot(series, aes(time, value, group = type)) +
  geom_col(aes(fill = type)) +
  geom_text(aes(label = type), position = "stack")

Trina

thanks! I had this issue that the stacking didn't work, and your solution nailed it – Jahdai

Answer 5

I have the exactly same problem today. You can get blue on top by using order=-as.numeric():

ggplot(ts, 
aes(z, x, fill=factor(y, levels=c("blue","white")), order=-as.numeric(y))) + 
geom_bar(stat = "identity")

Valuation

Answer 6

I had a similar issue and got around by changing the level of the factor. thought I'd share the code:

library(reshape2)
library(ggplot2)

group <- c(
  "1",
  "2-4",
  "5-9",
  "10-14",
  "15-19",
  "20-24",
  "25-29",
  "30-34",
  "35-39",
  "40-44",
  "45-49"
)

xx <- factor(group, levels(factor(group))[c(1, 4, 11, 2, 3, 5:10)])

method.1 <- c(36, 14, 8, 8, 18, 1, 46, 30, 62, 34, 34)
method.2 <- c(21, 37, 45, 42, 68, 41, 16, 81, 51, 62, 14)
method.3 <- c(37, 46, 18, 9, 16, 79, 46, 45, 70, 42, 28)  
elisa.neg <- c(12, 17, 18, 6, 19, 14, 13, 13, 7, 4, 1)  
elisa.eq <- c(3, 6, 3, 14, 1, 4, 11, 13, 5, 3, 2)

test  <- data.frame(person = xx, 
                    "Mixture Model" = method.1,
                    "Censoring" = method.3,
                    "ELISA neg" = elisa.neg,
                    "ELISA eqiv" = elisa.eq) 

melted <- melt(test, "person")
melted$cat <- ifelse(melted$variable == "Mixture.Model", "1",
                     ifelse(melted$variable == "Censoring", "2", "3"))

melted$variable = factor(melted$variable, levels = levels(melted$variable)[c(1, 2, 4,3 )]) ## This did the trick of changing the order

ggplot(melted, aes(x = cat, y = value, fill = variable)) + 
  geom_bar(stat = 'identity') + facet_wrap(~ person) +
  theme(axis.ticks.x=element_blank(),
        axis.text.x=element_blank()) + 
  labs(title = "My Title",
       y = "Per cent", x = "Age Group", fill = "")

(Sorry, this is my data, I didn't reproduce using the data from the original post, hope it's ok!)

Justinn