r - 如何通过符号大小控制 geom_errorbar 宽度？

Question

在下面的示例中，我有一个简单的平均值图，其中 X 轴和 Y 轴均带有标准差误差条。我想控制误差条宽度，以便两个轴始终绘制相同的尺寸。

理想情况下，我希望条形宽度/高度与符号大小相同(即在本例中 cex = 3)，与最终绘图尺寸无关。有办法做到这一点吗？

# Load required packages:
library(ggplot2)
library(plyr)

# Create dataset:
DF <- data.frame(
  group = rep(c("a", "b", "c", "d"),each=10),
  Ydata = c(seq(1,10,1),seq(5,50,5),seq(20,11,-1),seq(0.3,3,0.3)),
  Xdata = c(seq(1,10,1),seq(5,50,5),seq(20,11,-1),seq(0.3,3,0.3)))

# Summarise data:
subDF <- ddply(DF, .(group), summarise, 
                X = mean(Xdata), Y = mean(Ydata), 
                X_sd = sd(Xdata, na.rm = T), Y_sd = sd(Ydata))

# Plot data with error bars:
ggplot(subDF, aes(x = X, y = Y)) +
  geom_errorbar(aes(x = X, 
                ymin = (Y-Y_sd), 
                ymax = (Y+Y_sd)), 
                width = 1, size = 0.5) +
  geom_errorbarh(aes(x = X, 
                    xmin = (X-X_sd), 
                    xmax = (X+X_sd)), 
                height = 1, size = 0.5) +
  geom_point(cex = 3)  

以 1:1 比例 (500x500) 绘制时看起来不错:

但是当以 600x200 绘制时，误差条宽度/高度看起来有所不同

Answer 1

我会使用大小变量，这样您就可以同时控制所有 3 个绘图元素

geom_size <- 3

# Plot data with error bars:
ggplot(subDF, aes(x = X, y = Y)) +
  geom_errorbar(aes(x = X, 
                    ymin = (Y-Y_sd), 
                    ymax = (Y+Y_sd)), 
                width = 1, size = geom_size) +
  geom_errorbarh(aes(x = X, 
                     xmin = (X-X_sd), 
                     xmax = (X+X_sd)), 
                 height = 1, size = geom_size) +
  geom_point(cex = geom_size)