如何在R中自定义分组条形图的分组与图例排序？

要让分组和图例按before、during、after的顺序显示，核心是手动指定time因子的水平顺序，而非依赖默认的字母排序规则。

修改步骤 #

把原代码中df$time = as.factor(df$time)这一行，替换为手动定义因子水平的代码，明确指定你需要的顺序：

df$time = factor(df$time, levels = c("before", "during", "after"))

修改后的完整代码 #

df <- data.frame(time = c("after","before","during","before","after","before","during","after","after","during", "during","after","before","during","before"),
variable = c("granny", "red del", "other", "golden", "star", "granny", "red del", "other", "golden", "star", "granny", "red del", "other", "golden", "star"),
value = c(34,66,7,12,99,35,66,82,55,48, 27,55,82,42,26))

# 手动指定time因子的水平顺序
df$time = factor(df$time, levels = c("before", "during", "after"))
df$variable = as.factor(df$variable)

ggplot(df, aes(x = variable, y = value, fill = time)) + 
geom_bar(position='dodge', stat='identity') +
theme_minimal() +
labs(x=' ', y=' ', title=' ') +
theme(plot.title = element_text(hjust=0.5, size=20, face='bold')) +
theme_bw() + 
theme(axis.line = element_line(color='black'),
plot.background = element_blank(),
panel.grid.minor = element_blank(),
panel.grid.major = element_blank())

原理说明 #

默认as.factor()函数会按字母顺序为因子水平排序，所以after会排在最前。手动设置levels参数后，ggplot会严格遵循你指定的顺序渲染分组条形和图例。

内容的提问来源于stack exchange，提问作者ithoughtso