ggplot2: 为两个映射使用一个图例

Question

我正在制作一个包含两个不同映射的图表（“group”映射到颜色和线条类型，“to”映射到形状）。我想将这两个映射合并到一个图例中，但是无法在图例中正确显示形状。
以下是我的尝试：

set.seed(123)
plotdata = cbind.data.frame(x = rep(1:5, times = 4), 
                            y = rnorm(20), 
                            from = rep(c("1","2"), each = 10),
                            to = rep(c("1","2"), times= 10))
plotdata = cbind.data.frame(plotdata, group = paste0(plotdata$from, "to", plotdata$to))

library(ggplot2)

plot1 = ggplot(plotdata, aes(x = x, y = y, group = group, color = group, lty = group, shape = to)) +
  geom_point() + geom_line() + theme_bw() + 
  scale_color_discrete(name = "", 
                       breaks = c("1to1", "1to2", "2to1", "2to2"), 
                       labels = c("1to1", "1to2", "2to1", "2to2")) +
  scale_linetype_discrete(name = "", 
                          breaks = c("1to1", "1to2", "2to1", "2to2"), 
                          labels = c("1to1", "1to2", "2to1", "2to2")) +
  scale_shape_manual(name = "", 
                     values = c(1, 2, 1, 2),
                     breaks = c("1to1", "1to2", "2to1", "2to2"), 
                     labels = c("1to1", "1to2", "2to1", "2to2"))
print(plot1)

如您所见，我只有一个图例，但形状始终是圆形。
期望的行为：图例中的形状在圆形和金字塔之间交替显示，如图所示。

到目前为止，我尝试手动指定形状，但并没有帮助，如上所示。我还查看了我的绘图对象，希望能够操纵它，但无济于事。

- mts

Answer 1

您可以在不使用override.aes的情况下获得单个图例。只需将shape=group设置为同样的值，并使用scale_shape_manual设置重复形状值。在这种情况下，您不需要将to映射到任何内容，因为它包含的信息是多余的：

ggplot(plotdata, aes(x = x, y = y, group = group, color = group, lty = group, 
                     shape = group)) +
  geom_point() + geom_line() + theme_bw() + 
  scale_color_discrete(name = "") +
  scale_linetype_discrete(name = "") +
  scale_shape_manual(name = "", values=c(1,2,1,2))

- eipi10

Answer 2

这个问答帮助了我：你需要使用“override.aes”在颜色图例中明确指定形状：

plot1 = ggplot(plotdata, aes(x = x, y = y, group = group, color = group, lty = group, shape = to)) +
  geom_point() + geom_line() + theme_bw() + 
  scale_color_discrete(name = "", 
                       breaks = c("1to1", "1to2", "2to1", "2to2"), 
                       labels = c("1to1", "1to2", "2to1", "2to2"), 
                       guide = guide_legend(override.aes = list(shape = rep(c(1, 2), 2)))) +
  scale_linetype_discrete(name = "", 
                          breaks = c("1to1", "1to2", "2to1", "2to2"), 
                          labels = c("1to1", "1to2", "2to1", "2to2")) +
  scale_shape_discrete(guide = F)
plot1

请注意，您需要自己确定正确的形状。参考资料可能会有所帮助。

- mts