ggplot2 中的误差线和线条不匹配

Question

我在 ggplot2 中遇到错误栏问题。

我想绘制连续 [iv] 和标称 [条件] 变量之间的交互。 我用这样的代码

iv = 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(iv, condition, y)

lm20 <- lm(y ~ condition * iv, data = df)
summary(lm20) 

df$condition <- as.factor(df$condition)

ggeffect(lm20, terms = c("condition", "iv")) %>%  
  plot(show.title = FALSE) + 
  stat_summary(fun.y = mean,
               geom = "point") +
  stat_summary(fun.y = mean,
               geom = "line") +
  stat_summary(fun.data = mean_cl_boot,
               geom = "errorbar") +
  scale_y_continuous("Voting intentions", limits = c(0, 100)) + 
  scale_colour_discrete(name = "Control", labels = c("Low", "Medium", "High")) +
  scale_x_discrete("Condition", labels = c("Low","High")

这就是我得到的：

我遇到两个问题

1. 误差线和线不匹配
2. 我无法更改 X 轴上的标签

Answer 1

下面是一个只使用 ggplot2 的解决方案，所以没有那么优雅……看看它是否能解决问题！

# Create data frame with the effects    
df <- as.data.frame(ggeffect(lm20, terms = c("condition", "iv")))
# Add coordinates manually
df$x2 <- rep(1:2, 3) + rep(c(-.1,0,.1), each = 2)

# Plot
ggplot(df, aes(x2, predicted, col = group)) + 
  geom_errorbar(aes(x = x2, ymin = predicted-std.error, ymax = predicted+std.error), width = .1) +
  geom_segment(df %>% pivot_wider(id_cols = group, names_from = x,  values_from = c(predicted:conf.high, x2)),
               mapping = aes(x = x2_a, xend = x2_b, y = predicted_a, yend = predicted_b)) +
  geom_point(size = 2) +
  scale_color_discrete("Control",c("#9b2756", "#003054","#66b0a5"), labels=c("Low", "Medium", "High")) +
  scale_y_continuous("Voting intentions", limits = c(0, 100)) + 
  scale_x_continuous("Condition", breaks = 1:2, labels = c("Low","High"))

结果如下：

Answer 2

这里发生了几件事。主要是：

• 您需要设置一个 position_dodge 来替换您添加的点，因为 ggeffects 已经替换了错误栏
• ggeffects 实际上是使用连续的 x 轴刻度。请参阅下面我对scale_x_continuous() 的使用...
• mean_cl_boot 好像什么都没做，还没弄明白为什么

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

pd <- position_dodge(width=0.25)  ## width set by trial & error to match ggeffects plot
ggeffect(lm20, terms = c("condition", "iv")) %>%  
    plot(show.title = FALSE) +
    ## set large size/alpha to distinguish mean points from the 
    ##   (identical) points that ggeffects is already using for the estimated values
    stat_summary(fun = mean, geom = "point", position = pd, size = 5,
                 alpha=0.5) +
    stat_summary(fun = mean, geom = "line", position = pd) +
    stat_summary(fun.data = mean_cl_boot, geom = "errorbar",
                 position = pd, size = 5, alpha=0.5) +
    scale_y_continuous("Voting intentions", limits = c(0, 100)) + 
    scale_colour_discrete(name = "Control", labels = c("Low", "Medium", "High")) +
    scale_x_continuous(name = "Condition",
                       breaks = 1:2,
                       labels = c("Low","High"))