你能用离散的比例去除ggplot中轴和数据之间的空间吗

Question

是否可以在具有离散比例的 ggplot（点）中减少轴和数据之间的空间。我已经看到了很多使用离散比例执行此操作的方法，但似乎无法让它在这种情况下工作（轴上具有 1 个值的离散比例）。

我尝试转换为数字并使用基于 this response 的 expand(c(0,0)。它适用于 x 轴但不适用于 y 轴（可能是因为 y 上只有一个中断-轴？）

library(tidyverse)

df <- tibble(Site = rep("A", 4), 
             Basin = rep("B1", 4), 
             Variable = c("V1", "V2", "V3", "V4"), 
             cls = c("up", "down", "ns", "up"))

#basic plot (output above)
p <- ggplot(df , aes(x=Variable, y=Site)) +
  geom_point(size=3, aes(color=cls, shape=cls, fill=cls)) + 
  facet_grid(Basin~., scales="free", space="free")
p

#attempting to convert discrete scale to continuous and apply limits to axis
p2 <- ggplot(df , aes(x=Variable, y=c(as.numeric(factor(df$Site)))) +
  geom_point(size=3, aes(color=cls, shape=cls, fill=cls)) + 
  scale_y_continuous(limits=c(0.95,1.05),breaks=1,labels=levels(factor(df$Site)), expand=c(0,0))+
  facet_grid(Basin ~ ., scales="free", space="free")

#I have also tried using 
  scale_y_discrete(expand=expand_scale(mult = c(0.01, .01)))



#when same method is applied to the axis it seems to work - is this because there is more than 1 break/variable
 p3 <- ggplot(df , aes(x=as.numeric(df$Variable), y=as.numeric(factor(df$Site)))) +
  geom_point(size=3, aes(color=cls, shape=cls, fill=cls)) + 
  scale_x_continuous(limits=c(0.95,4.05),breaks=seq(1:length(unique(df$Variable))),labels=levels(factor(df$Variable)),
                      expand=c(0,0))+
  facet_grid(Basin~., scales="free", space="free")

Answer 1

您可以使用expand_scale() 调整轴的限制。 mult 参数将当前比例的最小值和最大值乘以你给它的百分比。 mult = c(0.2, 1) 表示将到底部的距离减少到当前距离的20%，并保持到顶部的距离为原始距离。

ggplot(df, aes(x = Variable, y = Site)) +
  geom_point(aes(color = cls, shape = cls, fill = cls), size = 3) +
  facet_grid(Basin ~ ., scales = "free", space = "free") +
  scale_y_discrete(expand = expand_scale(mult = c(0.2, 1)))