在ggplot2中创建自定义图例

如何解决在ggplot2中创建自定义图例

所以，这是我的问题。 我有类似于下面要使用ggplot2绘制的最小可重复示例的数据，其中一个数据框包含一个我想用作每个geom的x值的列，以及多个我想要不同的y值。从下面的示例中可以看到，我想将geom_line值的geom_point和geom_point与不同形状结合起来。

我现在的问题是，如何插入图例告诉我哪种形状代表什么列。到目前为止，从我对ggplot2的了解中，通常会生成一个图例，如果我将某个因子（可能不是正确的术语）映射到color =或group =上，我错了吗？那么如果没有那个先决条件，我怎么还能得到一个图例？

非常感谢您的帮助！

library(tidyverse)

df <- structure(list(rep = c(1,1,1),Y_1 = c(0.0198,0.0108,0.0117,0.00931,0.0089,0.0115,0.00509,0.00831,0.0158,0.0437,0.0953,0.267,0.677,1.81),Y_2 = c(0.025,0.00249,0.00303,0.00268,0.0102,0.0112,0.0231,0.0326,0.0575,0.0852,0.143,0.219,0.384,0.687,1.01),X = c(0.1,0.164,0.268,0.439,0.72,1.18,1.93,3.16,5.18,8.48,13.9,22.8,37.3,61.1,100)),row.names = c(NA,15L),class = "data.frame")

df_plot <- ggplot(data = df) +
  geom_line(mapping = aes(x = X,y = Y_1)) +
  geom_point(mapping = aes(x = X,y = Y_1),shape = 15) +
  geom_line(mapping = aes(x = X,y = Y_2)) +
  geom_point(mapping = aes(x = X,y = Y_2),shape = 0) +
  scale_x_log10() +
  scale_y_log10() +
  theme_classic()

df_plot

解决方法

创建图例的方法是将变量的不同级别映射到美学比例（在您的情况下为形状比例）。在ggplot中执行此操作的最惯用的方法是将Y_1和Y_2设为y值的一列，并用新的列来标记每个y根据它来自的原始列的值。这意味着您只需要一次调用geom_line和一次调用geom_point：

ggplot(data = tidyr::pivot_longer(df,c("Y_1","Y_2"))) +
  geom_line(mapping = aes(x = X,y = value,group = name)) +
  geom_point(mapping = aes(x = X,shape = name)) +
  scale_shape_manual(values = c(0,15)) +
  scale_x_log10() +
  scale_y_log10() +
  labs(shape = "variable") +
  theme_classic()