如何添加图例来指示颜色代码而不是数据？

Posted 2023-02-16

【中文标题】如何添加图例来指示颜色代码而不是数据？

【英文标题】：How can I add a legend to indicate a color code instead of data?

【发布时间】：2021-12-02 08:32:18

【问题描述】：

我正在努力为使用 PwrPlot() 函数创建的绘图添加颜色代码（图例），如下所示。这是一个教学演示，我只需要将标签 (alpha, beta, 1-alpha, 1-beta) 替换为说明每种颜色所指的图例（实际上，更改曲线的参数可能会导致一些'图中的“丑陋”标签位置！）。运行此函数还会发出我无法解释的警告：

警告信息： 1：在 is.na(x) 中： is.na() 应用于“表达式”类型的非（列表或向量）

任何帮助将不胜感激！谢谢

    PwrPlot <- function(mu0=0, mu1=1.9, sig0=1, sig1=1, alpha=0.05, tail=1)
  ggplot(data.frame(x = -4:5), aes(x)) + 
    stat_function(fun = dnorm, args = c(mu0, sig0), geom = 'area', 
                  xlim = c(qnorm(1-alpha/tail, mu0, sig0), 5), fill = 'red') + 
    stat_function(fun = dnorm, args = c(mu0, sig0)) +
    stat_function(fun = dnorm, args = c(mu0, sig0), geom = 'area', 
                  xlim = c(-4, qnorm(1-alpha/tail, mu0, sig0)), fill = 'deepskyblue3') + 
    stat_function(fun = dnorm, args = c(mu0, sig0)) +
    stat_function(fun = dnorm, args = c(mu1, sig1)) +
    stat_function(fun = dnorm, args = c(mu1, sig1), geom = 'area', 
                  xlim = c(qnorm(1-alpha/tail, mu0, sig0), 5), fill = 'cyan4', alpha=0.2) +
    stat_function(fun = dnorm, args = c(mu1, sig1), geom = 'area', 
                  xlim = c(-4, qnorm(1-alpha/tail, mu0, sig0)), fill = 'chocolate3', alpha=0.5) +

    geom_text(x=-0.4, y=0.18, label=expression(1-alpha), size=10, col="white") +
    geom_text(x=2, y=0.018, label=expression(alpha), size=10, col="white") +
    geom_text(x=1, y=0.1, label=expression(beta), size=10, col="white") +
    geom_text(x=2.5, y=0.1, label=expression(1-beta), size=10, col="black") +
    geom_text(x=-1.7, y=0.35, label="H0", size=10, col="black") +
    geom_text(x=3.5, y=0.35, label="H1", size=10, col="black") +
    labs(y="Densité") 

PwrPlot()

【问题讨论】：

非常感谢！这解决了这个问题，我可以继续前进！

【参考方案1】：

你可以把颜色放在aes()里面，结合scale_fill_identity()就可以构造一个图例。

library(ggplot2)

PwrPlot <- function(mu0=0, mu1=1.9, sig0=1, sig1=1, alpha=0.05, tail=1)
  ggplot(data.frame(x = -4:5), aes(x)) + 
    stat_function(fun = dnorm, args = c(mu0, sig0), geom = 'area', 
                  xlim = c(qnorm(1-alpha/tail, mu0, sig0), 5), 
                  aes(fill = 'red')) + 
    stat_function(fun = dnorm, args = c(mu0, sig0)) +
    stat_function(fun = dnorm, args = c(mu0, sig0), geom = 'area', 
                  xlim = c(-4, qnorm(1-alpha/tail, mu0, sig0)), 
                  aes(fill = 'deepskyblue3')) + 
    stat_function(fun = dnorm, args = c(mu0, sig0)) +
    stat_function(fun = dnorm, args = c(mu1, sig1)) +
    stat_function(fun = dnorm, args = c(mu1, sig1), geom = 'area', 
                  xlim = c(qnorm(1-alpha/tail, mu0, sig0), 5), 
                  aes(fill = 'cyan4'), alpha=0.2) +
    stat_function(fun = dnorm, args = c(mu1, sig1), geom = 'area',
                  xlim = c(-4, qnorm(1-alpha/tail, mu0, sig0)),
                  aes(fill = 'chocolate3'), alpha=0.5) +
    scale_fill_identity(
      labels = expression(beta, 1-alpha, 1-beta, alpha),
      guide = guide_legend()
    ) +
    annotate(
      "text", size = 10,
      x = c(-0.4, 2, 1, 2.5, -1.7, 3.5),
      y = c(0.18, 0.018, 0.1, 0.1, 0.35, 0.35),
      label = expression(1-alpha, alpha, beta, 1-beta, "H0", "H1"),
      colour = rep(c("white", "black"), each = 3)
    ) +
    labs(y="Densité") 

PwrPlot()
#> Warning in is.na(x): is.na() applied to non-(list or vector) of type
#> 'expression'

^{由reprex package (v2.0.1) 于 2021 年 10 月 14 日创建}