ggplot2：离散值之间的网格线

Question

当使用离散值时，ggplot2在值的中心处的刻度值处提供网格线

library(reshape2)

ggplot(data=tips, aes(x=time, y=total_bill, fill=sex)) +
    geom_bar(stat="identity", position=position_dodge())

如何设置x轴的网格线以显示在离散值之间（即'Dinner'和'Lunch'之间）

我试图设置panel.grid.minor.x但是（我认为）因为它是离散的，这不起作用...这不是一个小的值来绘制girdline。

ggplot(data=tips, aes(x=time, y=total_bill, fill=sex)) +
    geom_bar(stat="identity", position=position_dodge()) + 
    theme(panel.grid.minor.x = element_line())

Answer 1

您可以添加一条垂直线作为网格线，如下所示：

geom_vline(xintercept=1.5, colour='white')

当然，您可以根据需要更改线宽，颜色，样式等，如果有多组需要用网格线分隔的条形，则可以在适当的位置添加多条线。例如，使用一些假数据：

set.seed(1)
dat = data.frame(total_bill=rnorm(100,80,10), 
                 sex=rep(c("Male","Female"),50),
                 time=sample(c("Breakfast","Brunch","Lunch","Afternoon Tea","Dinner"), 
                             100, replace=TRUE))
dat$time = factor(dat$time, 
                  levels=c("Breakfast","Brunch","Lunch","Afternoon Tea","Dinner"),
                  ordered=TRUE)

ggplot(data=dat, aes(x=time, y=total_bill, fill=sex)) +
  geom_bar(stat="identity", position=position_dodge()) +
  geom_vline(xintercept=seq(1.5, length(unique(dat$time))-0.5, 1), 
             lwd=1, colour="black")

Answer 2

遇到了同样的问题。我的解决方案是使网格线更大..

set.seed(1)
dat = data.frame(total_bill=rnorm(100,80,10), 
                 sex=rep(c("Male","Female"),50),
                 time=sample(c("Breakfast","Brunch","Lunch","Afternoon Tea","Dinner"), 
                             100, replace=TRUE))
dat$time = factor(dat$time, 
                  levels=c("Breakfast","Brunch","Lunch","Afternoon Tea","Dinner"),
                  ordered=TRUE)

ggplot(data=dat, aes(x=time, y=total_bill, color=sex)) +
  geom_point(stat="identity", position=position_dodge()) +
  theme(panel.grid.major.x = element_line(color = "white", size = 20))