Using the answer to this question, how can I plot percentage labels conditionally, say I only want them to appear on the plot if percentages are less than 50%? Or better, if I want to see the percentages associated with one category only?
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1 Answer
I started with a slightly different solution than you linked to, because I found the syntax in that example a little murky (although it is shorter). Then I create columns for the labels and their y positions, and plot the labels using geom_text().
require(ggplot2)
require(plyr)
#set up the data frame, as in the previous example
cls.grp <- gl(n=4,k=20,labels=c("group a","group b","group c", "group d"))
ser <- sample(x=c("neg","pos"),size=80,replace=TRUE, prob=c(30,70))
syrclia <- data.frame(cls.grp,ser)
#create a data frame with the 'metadata' you will plot
ct <- ddply(syrclia, "cls.grp", count) #count the occurrences of each cls.group type
ct <- ddply(ct, "cls.grp", transform, frac=freq/sum(freq)*100) #calculate frequencies as percentages
ct$frac_to_print <- ""
cutoff <- 30 #define the cutoff, below which you will not plot percentages
ct$frac_to_print[which(ct$frac > cutoff)] <- paste(ct$frac[which(ct$frac>cutoff)], "%")
ct <- ddply(ct, "cls.grp", transform, pos = cumsum(freq)) #calculate the position for each label
ggplot(ct, aes(x=cls.grp, y=freq)) +
geom_bar(aes(fill=ser)) +
geom_text(aes(x=cls.grp, y=pos, label=frac_to_print))
