无法修改ggplot图例标题及图例显示异常问题求助

问题说明 #

• 无法修改ggplot图表的图例标题，尝试scale_color_discrete、labs(color=...)等方法均无效
• 在geom_point的aes参数中设置size=2后，图例出现多余的尺寸标识

可复现代码 #

## 创建数据框
Predictor <- c("No", "Yes", "No", "Yes")
TimePoint <- c("Pre", "Pre", "Post", "Post")
value <- c(33, 32, 31, 40)
SE <- c(1.5, 1.5, 1.5, 1.5)
# 注：原代码中此处的estimate应为value，属于笔误，修正后才能正常运行
dataframe <- data.frame(Predictor, TimePoint, value, SE)

## 定义因子并重新排序TimePoint的水平
dataframe$TimePoint <- as.factor(dataframe$TimePoint)
dataframe$Predictor <- as.factor(dataframe$Predictor)
dataframe$TimePoint = factor(dataframe$TimePoint, levels = c("Pre", "Post"), ordered = TRUE)

## 创建图表
ggp <- ggplot(data=dataframe, aes(x=TimePoint, y=value, group=Predictor)) +
  geom_errorbar(aes(ymin=value-SE, ymax=value+SE), width=.1) +
  geom_line()+
  geom_point(aes(shape=Predictor, size=2)) +
  coord_cartesian(ylim = c(0, 50)) + ## 指定y轴上下限
  ylab("Value") +
  xlab("
       Timing")+
  scale_x_discrete(expand = c(0,0.25)) +
  scale_y_continuous(breaks = seq(0, 50, 5), limits = c(0, 50), expand = c(0, 0)) +
  theme_classic() +
  theme(axis.line = element_line(size = .6, colour = "black", linetype=1),         
        axis.text = element_text( angle = 0, color="black", size=18, face=2),
        axis.title.x = element_text(color="black", size=18, face=2),
        axis.title.y = element_text(color="black", size=18, face=2, margin=margin(r=20)))

print(ggp)

已尝试方法 #

ggp + scale_color_discrete(name = "New Legend Title")

ggp + labs(color = "New Legend Title")

ggp + scale_fill_discrete(name="New Legend Title")

ggp + guides(col = guide_color(title = "New Legend Title"))

ggp + labs(color = "New Legend Title")

解决方案 #

1. 移除多余的尺寸标识 #

aes()内部的参数是用来映射数据变量的，固定尺寸不需要放在映射里，把size=2移到geom_point()外部即可：

geom_point(aes(shape=Predictor), size=2)

2. 修改图例标题 #

当前图例是由shape映射生成的，之前的方法无效是因为错用了color/fill相关的设置，需要针对shape操作，两种可选方法：

方法一：用labs()直接指定

ggp + labs(shape = "新图例标题")

方法二：用scale_shape_discrete()设置

ggp + scale_shape_discrete(name = "新图例标题")

完整修正代码 #

## 创建数据框
Predictor <- c("No", "Yes", "No", "Yes")
TimePoint <- c("Pre", "Pre", "Post", "Post")
value <- c(33, 32, 31, 40)
SE <- c(1.5, 1.5, 1.5, 1.5)
dataframe <- data.frame(Predictor, TimePoint, value, SE)

## 定义因子并重新排序TimePoint的水平
dataframe$TimePoint <- as.factor(dataframe$TimePoint)
dataframe$Predictor <- as.factor(dataframe$Predictor)
dataframe$TimePoint = factor(dataframe$TimePoint, levels = c("Pre", "Post"), ordered = TRUE)

## 创建图表
ggp <- ggplot(data=dataframe, aes(x=TimePoint, y=value, group=Predictor)) +
  geom_errorbar(aes(ymin=value-SE, ymax=value+SE), width=.1) +
  geom_line()+
  geom_point(aes(shape=Predictor), size=2) + # 修正size的位置
  coord_cartesian(ylim = c(0, 50)) +
  ylab("Value") +
  xlab("Timing") + # 移除多余换行
  scale_x_discrete(expand = c(0,0.25)) +
  scale_y_continuous(breaks = seq(0, 50, 5), limits = c(0, 50), expand = c(0, 0)) +
  theme_classic() +
  theme(axis.line = element_line(size = .6, colour = "black", linetype=1),         
        axis.text = element_text( angle = 0, color="black", size=18, face=2),
        axis.title.x = element_text(color="black", size=18, face=2),
        axis.title.y = element_text(color="black", size=18, face=2, margin=margin(r=20))) +
  labs(shape = "分组") # 修改图例标题

print(ggp)

内容的提问来源于stack exchange，提问作者KG202