在ggplot2图表中更改误差条的颜色。

Question

我在ggplot中的条形图中遇到了误差棒问题。 我有一个分类（条件）和连续（调节变量）变量之间的交互作用。我想显示误差棒，但它们与条形图颜色相同，这使它们难以解释。 我尝试为误差棒添加color =“black”等颜色，但它不会改变任何东西。 以下是代码：

moderator = runif(n = 100, min = 1, max = 7)
condition <- rep(letters[1:2], length.out = 100)
y = runif(n = 100, min = 1, max = 100)

df <- data.frame(moderator, condition, y)


lm21 <- lm(y~ condition* moderator, data = df)
summary(lm21) 

library(ggeffects)
library(ggplot2)
library(magrittr)


    pd <- position_dodge() 
ggeffect(lm21, terms = c("condition", "moderator")) %>%  
  plot(show.title = FALSE) +
  stat_summary(fun.y = mean, geom = "bar", position = pd, width = 0.25) +
  stat_summary(fun.data = mean_cl_boot, geom = "errorbar",
               position = pd, size = 8.5, alpha=13.2) +
  scale_y_continuous("Voting", limits = c(0, 100)) + 
  scale_color_discrete(name = "Control", labels = c("Low", "Medium", "High")) +
  scale_x_continuous(name = "Condition",
                     breaks = 0:1,
                     labels = c("Low","High")) 

图形如下所示：

如何改变误差线的颜色，以便它们完全可见？

提前致谢！

- Anna Potoczek

Answer 1

我试图将ggeffect值转换为数据框，最终结果如下，希望这是你所想要的。 抱歉，宽度控制是手动完成的，我尝试调整以使其居中。也许有人比我更擅长，知道如何操作。

  ggplot(as.data.frame(ggeffect(lm21, terms = c("condition", "moderator"))), aes(x = factor(x))) +
    geom_col(aes(y = predicted, fill = factor(group)), position = position_dodge2(width = .5, preserve = "single", padding = 0)) +
    geom_errorbar(aes(ymin = conf.low, ymax = conf.high, group = factor(group)), position = position_dodge(width = .9), width = .15) +
    geom_point(aes(y = predicted, group = factor(group)), position = position_dodge2(width = .9)) +
    scale_fill_discrete(name = "Control", labels = c("Low", "Medium", "High")) +
    scale_y_continuous("Voting", limits = c(0, 100)) +
    scale_x_discrete(name = "Condition", labels = c("Low","High")) +
    theme_light()

- Guillaume Mulier

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太棒了，完美地运行！非常感谢你！ - Anna Potoczek

Answer 2

好的，虽然这不是最简单的方法，但这是我所做的：

p = ggeffect(lm21, terms = c("condition", "moderator")) %>%  
  plot(show.title = FALSE) +
  stat_summary(fun.y = mean, geom = "bar", position = pd, width = 0.25) +
  stat_summary(fun.data = mean_cl_boot, geom = "errorbar",
               position = pd, size = 8.5, alpha=13.2) +
  scale_y_continuous("Voting", limits = c(0, 100)) + 
  scale_color_discrete(name = "Control", labels = c("Low", "Medium", "High")) +
  scale_x_continuous(name = "Condition",
                     breaks = 0:1,
                     labels = c("Low","High"))+
  scale_colour_manual(values = rep('black',3))+
  theme(legend.position = 'none') 

输出结果如下：

唯一的问题是图例已经丢失，因为scale_colour_manual改变了它。但是您可以使用此帖子提取图例How to plot just the legends in ggplot2? 并将其与您的图形合并。

我希望这就是您想要的。

- elielink

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谢谢您的回答，我一定会尝试这个方法。不过，是否也可以添加误差条的下部分，例如这里的图片？ https://pythonforundergradengineers.com/images/bar_plot_with_error_bars.png - Anna Potoczek

Answer 3

这是另一种基于grobs操作的解决方案。

p <- ggeffect(lm21, terms = c("condition", "moderator")) %>%  
  plot(show.title = FALSE) +
  stat_summary(fun.y = mean, geom = "bar", position = pd, width = 0.25) +
  stat_summary(fun.data = mean_cl_boot, geom = "errorbar",
               position = pd, size = 8.5, alpha=13.2) +
  scale_y_continuous("Voting", limits = c(0, 100)) + 
  scale_color_discrete(name = "Control", labels = c("Low", "Medium", "High")) +
  scale_x_continuous(name = "Condition",
                     breaks = 0:1,
                     labels = c("Low","High")) 

# Change the order of ggplot layers (error bars are printed after mean bars)
p$layers <- p$layers[c(3,1,2,4)]

# Set colors of polyline grob (error bars)
q <- ggplotGrob(p)
q$grobs[[6]]$children[[5]]$gp$col <- rep("black",6)
grid::grid.draw(q)

- Marco Sandri