通过交互和指南修改 ggplot2 中的图例

df <- data.frame(Depth = c(1, 2, 3, 4, 5, 6, 7, 8), 
                 Var1 = as.factor(c(rep("A", 4), rep("B", 4))),
                 Var2 = as.factor(c(rep(c("C", "D"), 4))),
                 Value = runif(8))


g <- ggplot(df, aes(Depth, Value, col = Var1, shape = Var2, lty = Var2))+
  geom_path(aes(group = interaction(Var1, Var2)), size = 0.5) +
  geom_point(aes(group = interaction(Var1, Var2)), size = 1)+
  scale_shape_manual(values = c(16, 5))+
  ylab("Depth [cmbsf]")

g + guides(colour = guide_legend(override.aes = list(shape = 15, size = 4, linetype = 0)),
           shape = guide_legend(override.aes = list(size = 4)))

我想修改图例Var2。我只想增加形状的大小，而不是线条的大小。不幸的是，size形状指南中的参数也适用于线型。

如果我添加另一个线型指南：

g + guides(colour = guide_legend(override.aes = list(shape = 15, size = 4, linetype = 0)),
           shape = guide_legend(override.aes = list(size = 4)),         
           lty = guide_legend(override.aes = list(size=1)))

I get:

Warning message:
In guide_merge.legend(init, x[[i]]) : Duplicated override.aes is ignored.

如何解开用于图例的参考线？

可能有点矫枉过正，但我​​们可以创造一个替代方案geom_path()图例密钥大小硬编码为 0.5：

ggplot(df, aes(Depth, Value, col = Var1, shape = Var2, lty = Var2)) +
  geom_path2(aes(group = interaction(Var1, Var2)), size = 0.5) +
  geom_point(aes(group = interaction(Var1, Var2)), size = 1) +
  scale_shape_manual(values = c(16, 5)) +
  ylab("Depth [cmbsf]") +
  guides(colour = guide_legend(override.aes = list(shape = 15, size = 4, linetype = 0)),
         shape = guide_legend(override.aes = list(size = 4)))

所需代码geom_path2():

library(grid)

# Create new ggproto object that inherits from GeomPath, 
# except for its draw_key function
GeomPath2 <- ggproto("GeomPath2",
                     GeomPath,
                     draw_key = function (data, params, size) {
                       data$linetype[is.na(data$linetype)] <- 0
                       segmentsGrob(0.1, 0.5, 0.9, 0.5, 
                                    gp = gpar(col = alpha(data$colour, data$alpha), 
                                              lwd = 0.5 * .pt, # originally lwd = data$size * .pt
                                              lty = data$linetype, 
                                              lineend = "butt"), 
                                    arrow = params$arrow)
                     })

# define geom_path2 to be exactly the same as geom_path, except that
# it uses Geom = GeomPath2 instead of Geom = GeomPath
geom_path2 <- function (mapping = NULL, data = NULL, stat = "identity", position = "identity", 
                        ..., lineend = "butt", linejoin = "round", linemitre = 10, 
                        arrow = NULL, na.rm = FALSE, show.legend = NA, inherit.aes = TRUE) {
  layer(data = data, mapping = mapping, stat = stat, 
        geom = GeomPath2, # originally GeomPath
        position = position, show.legend = show.legend, inherit.aes = inherit.aes, 
        params = list(lineend = lineend, linejoin = linejoin, 
                      linemitre = linemitre, arrow = arrow, na.rm = na.rm, 
                      ...))
  }