MYaseen208 MYaseen208 - 1 month ago 19
R Question

Showing data values on stacked bar chart in ggplot2

I'd like to show data values on stacked bar chart in ggplot2. Here is my attempted code

Year <- c(rep(c("2006-07", "2007-08", "2008-09", "2009-10"), each = 4))
Category <- c(rep(c("A", "B", "C", "D"), times = 4))
Frequency <- c(168, 259, 226, 340, 216, 431, 319, 368, 423, 645, 234, 685, 166, 467, 274, 251)
Data <- data.frame(Year, Category, Frequency)
library(ggplot2)
p <- qplot(Year, Frequency, data = Data, geom = "bar", fill = Category, theme_set(theme_bw()))
p + geom_text(aes(label = Frequency), size = 3, hjust = 0.5, vjust = 3, position = "stack")


enter image description here

I'd like to show these data values in the middle of each portion. Any help in this regard will be highly appreciated. Thanks

Answer

Here is one approach, which calculates the midpoints of the bars.

library(ggplot2)
library(plyr)

# calculate midpoints of bars (simplified using comment by @DWin)
Data <- ddply(Data, .(Year), 
   transform, pos = cumsum(Frequency) - (0.5 * Frequency)
)

# library(dplyr) ## If using dplyr... 
# Data <- group_by(Data,Year) %>%
#    mutate(pos = cumsum(Frequency) - (0.5 * Frequency))

# plot bars and add text
p <- ggplot(Data, aes(x = Year, y = Frequency)) +
     geom_bar(aes(fill = Category), stat="identity") +
     geom_text(aes(label = Frequency, y = pos), size = 3)

Resultant chart

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