如何在ggplot直方图中修改坐标轴线条的粗细？

问题原因 #

你尝试用panel.border设置时，**未指定fill=NA**导致矩形填充覆盖了整个绘图区域，且size=5线条过粗，才出现图形消失的问题。

原始代码 #

library(tidyverse)

iris %>% 
  ggplot(aes(x=Sepal.Length))+
  geom_histogram(bins=10,
                 fill="white",
                 color="black",
                 size=1)+
  labs(x="Sepal Length",
       y="Count",
       title = "Sepal Length Histogram")+
  theme_classic()+
  theme(plot.title = element_text(face="bold"))+
  scale_x_continuous(expand = c(0.01,0.01))+
  scale_y_continuous(expand = c(0.00,0.01))

正确实现方式 #

方式1：直接加粗坐标轴线条（适配theme_classic()） #

theme_classic()默认显示独立的坐标轴线条，直接修改axis.line的参数即可，这是最简洁的方法：

library(tidyverse)

iris %>% 
  ggplot(aes(x=Sepal.Length))+
  geom_histogram(bins=10,
                 fill="white",
                 color="black",
                 size=1)+
  labs(x="Sepal Length",
       y="Count",
       title = "Sepal Length Histogram")+
  theme_classic()+
  theme(plot.title = element_text(face="bold"),
        # 统一加粗X/Y轴线条，size值可按需调整
        axis.line = element_line(color = "black", size = 2))+
  scale_x_continuous(expand = c(0.01,0.01))+
  scale_y_continuous(expand = c(0.00,0.01))

如果需要单独设置X/Y轴粗细，可拆分参数：

theme(plot.title = element_text(face="bold"),
      axis.line.x = element_line(color = "black", size = 2),
      axis.line.y = element_line(color = "black", size = 2))

方式2：使用面板边框（若需要完整边框效果） #

如果想要的是完整的面板边框样式，需给panel.border添加fill=NA避免覆盖图形，同时调整合适的线条粗细：

library(tidyverse)

iris %>% 
  ggplot(aes(x=Sepal.Length))+
  geom_histogram(bins=10,
                 fill="white",
                 color="black",
                 size=1)+
  labs(x="Sepal Length",
       y="Count",
       title = "Sepal Length Histogram")+
  theme_classic()+
  theme(plot.title = element_text(face="bold"),
        panel.border = element_rect(linetype = "solid",
                                    colour = "black", 
                                    size=2,
                                    fill=NA))+ # 关键：设置fill=NA防止覆盖图形
  scale_x_continuous(expand = c(0.01,0.01))+
  scale_y_continuous(expand = c(0.00,0.01))

注：使用面板边框时，可添加axis.line = element_blank()隐藏原有坐标轴线条，避免线条重叠。

内容的提问来源于stack exchange，提问作者Shawn Hemelstrand