ggplot、facet、piechart:将文本放置在饼图切片的中间 [英] ggplot, facet, piechart: placing text in the middle of pie chart slices

问题描述

我正在尝试使用 ggplot 生成一个多面饼图，但在将文本放置在每个切片的中间时遇到了问题:

dat = read.table(text = "Channel Volume Cnt代理高8344代理中号 5448代理低23823KIOSK 高19275KIOSK 中号 13554KIOSK 低 38293", 标头 = TRUE)vis = ggplot(data=dat, aes(x=factor(1), y=Cnt, fill=Volume)) +geom_bar(stat="identity", position="fill") +coord_polar(theta="y") +facet_grid(Channel~.) +geom_text(aes(x=factor(1), y=Cnt, label=Cnt, ymax=Cnt),位置=位置填充(宽度=1))

输出:

geom_text 需要调整哪些参数，才能在饼图切片中间放置数字标签?

相关问题是, plyr 或 dplyr 包:

第 1 步:为每个频道创建位置变量

# 以 R 为基础dat$pos <- with(dat, ave(Cnt, Channel, FUN = function(x) cumsum(x) - 0.5*x))# 使用 data.table 包图书馆(数据表)设置DT(数据)dat <- dat[, pos:=cumsum(Cnt)-0.5*Cnt, by="Channel"]# 使用 plyr 包图书馆(plyr)dat <- ddply(dat, .(Channel), 变换, pos=cumsum(Cnt)-0.5*Cnt)# 使用 dplyr 包图书馆(dplyr)dat <- dat %>% group_by(Channel) %>% mutate(pos=cumsum(Cnt)-0.5*Cnt)

第 2 步:创建分面图

库(ggplot2)ggplot(数据 = 数据)+geom_bar(aes(x = "", y = Cnt, fill = Volume), stat = "identity") +geom_text(aes(x = "", y = pos, label = Cnt)) +coord_polar(theta = "y") +facet_grid(Channel ~ ., scales = "free")

结果:

I'm trying to produce a facetted pie-chart with ggplot and facing problems with placing text in the middle of each slice:

dat = read.table(text = "Channel Volume Cnt
                         AGENT   high   8344
                         AGENT medium   5448
                         AGENT    low  23823
                         KIOSK   high  19275
                         KIOSK medium  13554
                         KIOSK    low  38293", header=TRUE)

vis = ggplot(data=dat, aes(x=factor(1), y=Cnt, fill=Volume)) +
  geom_bar(stat="identity", position="fill") +
  coord_polar(theta="y") +
  facet_grid(Channel~.) +
  geom_text(aes(x=factor(1), y=Cnt, label=Cnt, ymax=Cnt), 
            position=position_fill(width=1))

The output:

What parameters of geom_text should be adjusted in order to place numerical labels in the middle of piechart slices?

Related question is Pie plot getting its text on top of each other but it doesn't handle case with facet.

UPDATE: following Paul Hiemstra advice and approach in the question above I changed code as follows:

---> pie_text = dat$Cnt/2 + c(0,cumsum(dat$Cnt)[-length(dat$Cnt)])

     vis = ggplot(data=dat, aes(x=factor(1), y=Cnt, fill=Volume)) +
     geom_bar(stat="identity", position="fill") +
     coord_polar(theta="y") +
     facet_grid(Channel~.) +
     geom_text(aes(x=factor(1), 
--->               y=pie_text, 
                   label=Cnt, ymax=Cnt), position=position_fill(width=1))

As I expected tweaking text coordiantes is absolute but it needs be within facet data:

解决方案

NEW ANSWER: With the introduction of ggplot2 v2.2.0, position_stack() can be used to position the labels without the need to calculate a position variable first. The following code will give you the same result as the old answer:

ggplot(data = dat, aes(x = "", y = Cnt, fill = Volume)) + 
  geom_bar(stat = "identity") +
  geom_text(aes(label = Cnt), position = position_stack(vjust = 0.5)) +
  coord_polar(theta = "y") +
  facet_grid(Channel ~ ., scales = "free")

To remove "hollow" center, adapt the code to:

ggplot(data = dat, aes(x = 0, y = Cnt, fill = Volume)) + 
  geom_bar(stat = "identity") +
  geom_text(aes(label = Cnt), position = position_stack(vjust = 0.5)) +
  scale_x_continuous(expand = c(0,0)) +
  coord_polar(theta = "y") +
  facet_grid(Channel ~ ., scales = "free")

---

OLD ANSWER: The solution to this problem is creating a position variable, which can be done quite easily with base R or with the data.table, plyr or dplyr packages:

Step 1: Creating the position variable for each Channel

# with base R
dat$pos <- with(dat, ave(Cnt, Channel, FUN = function(x) cumsum(x) - 0.5*x))

# with the data.table package
library(data.table)
setDT(dat)
dat <- dat[, pos:=cumsum(Cnt)-0.5*Cnt, by="Channel"]

# with the plyr package
library(plyr)
dat <- ddply(dat, .(Channel), transform, pos=cumsum(Cnt)-0.5*Cnt)

# with the dplyr package
library(dplyr)
dat <- dat %>% group_by(Channel) %>% mutate(pos=cumsum(Cnt)-0.5*Cnt)

Step 2: Creating the facetted plot

library(ggplot2)
ggplot(data = dat) + 
  geom_bar(aes(x = "", y = Cnt, fill = Volume), stat = "identity") +
  geom_text(aes(x = "", y = pos, label = Cnt)) +
  coord_polar(theta = "y") +
  facet_grid(Channel ~ ., scales = "free") 

The result:

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