R：带有ggplot2的条件标签

Question

使用this question 的答案，我如何有条件地绘制百分比标签，比如说我只希望它们出现在百分比小于 50% 的情况下？或者更好的是，如果我只想查看与一个类别相关的百分比？

Answer 1

我从与您链接的解决方案略有不同的解决方案开始，因为我发现该示例中的语法有点模糊（尽管它更短）。然后我为标签及其 y 位置创建列，并使用geom_text() 绘制标签。

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))