强制 y 轴从 0 开始，插入“break”，并使用 ggplot2 有一个大的 y 轴

Question

我仍在努力最终确定一个可复制的数字以供出版。审阅者希望看到下图的 y 轴从 0 开始并包含换行符“//”。y 轴不仅需要非常大（例如 1500 个单位），而且还需要非常紧密地放大（例如 300 个单位）。这使得审阅者希望我们添加一个换行符来表示我们的轴从 0 开始，但继续。

我可以创建的示例：

我想要的示例（注意 y 轴；这是在类似图中的 powerpoint 中手动完成的）：

我的代码：

ggplot(data = quad2,
       aes(x, predicted, group = group)) +
  geom_point(aes(shape = group), size = 6) +
  scale_shape_manual(values=c(19, 1)) +
  geom_line(size = 2,
            aes(linetype = group),
            color = "black") +
  scale_linetype_manual(values = c("solid", "dashed")) +
  geom_linerange(size = 1,
                 aes(ymin = predicted - conf.low,
                     ymax = predicted + conf.high),
                 color = "black",
                 alpha = .8) +
   geom_segment(aes(xend = x,
                    yend = ifelse(group == "Control", conf.high, conf.low)),
                arrow = arrow(angle = 90), color = "red")+
    labs(x = "Time",
       y = expression(bold("QUAD Volume (cm"^"3"*")")),
       linetype = "",
       shape = "") + #Legend title
  scale_y_continuous(limits =c(1500, 2000)) 

可重现的数据：

dput(quad2)
structure(list(x = structure(c(1L, 1L, 2L, 2L, 3L, 3L, 4L, 4L, 
5L, 5L), .Label = c("PRE", "MID1", "MID2", "MID3", "POST"), class = "factor"), 
    predicted = c(1666.97185871754, 1660.27445165342, 1743.2831065274, 
    1678.48945165342, 1788.50605542978, 1637.40907049806, 1807.55826371403, 
    1639.78265640012, 1865.8766220711, 1652.91070173056), std.error = c(88.8033117577884, 
    91.257045996107, 92.9973963841595, 95.3834973421298, 95.0283457128716, 
    97.3739053806999, 95.6466346849776, 97.9142418717957, 93.3512943191676, 
    95.5735155125126), conf.low = c(0, 91.257045996107, 0, 95.3834973421298, 
    0, 97.3739053806999, 0, 97.9142418717957, 0, 95.5735155125126
    ), conf.high = c(88.8033117577884, 0, 92.9973963841595, 0, 
    95.0283457128716, 0, 95.6466346849776, 0, 93.3512943191676, 
    0), group = structure(c(1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 
    2L), .Label = c("Intervention", "Control"), class = "factor")), class = "data.frame", row.names = c(NA, 
-10L))

Answer 1

绘制不连续轴变得困难是有原因的，这个原因是您应该尽可能避免这样做。虽然我不同意你的审稿人的观点，但如果你真的想要 y 轴中断，你可以对底层网格图形进行深入研究。

首先制定你的情节。我唯一添加的是 y 轴格式和轴线主题。我们只需将底部的勾号标记为“0”。

plt <- ggplot(data = quad2,
       aes(x, predicted, group = group)) +
  geom_point(aes(shape = group), size = 6) +
  scale_shape_manual(values=c(19, 1)) +
  geom_line(size = 2,
            aes(linetype = group),
            color = "black") +
  scale_linetype_manual(values = c("solid", "dashed")) +
  geom_linerange(size = 1,
                 aes(ymin = predicted - conf.low,
                     ymax = predicted + conf.high),
                 color = "black",
                 alpha = .8) +
  geom_segment(aes(xend = x,
                   yend = ifelse(group == "Control", conf.high, conf.low)),
               arrow = arrow(angle = 90), color = "red")+
  labs(x = "Time",
       y = expression(bold("QUAD Volume (cm"^"3"*")")),
       linetype = "",
       shape = "") + #Legend title
  scale_y_continuous(limits =c(1400, 2000),
                     breaks = seq(1400, 2000, by = 200),
                     labels = c(0, seq(1600, 2000, by = 200)),
                     expand = c(0,0,0.05,0)) +
  theme(axis.line = element_line())

然后，我们将其放入 gtable 中并获取 y 轴线：

gt <- ggplotGrob(plt)

is_yaxis <- which(gt$layout$name == "axis-l")
yaxis <- gt$grobs[[is_yaxis]]

# You should grab the polyline child
yline <- yaxis$children[[1]]

现在我们可以根据需要编辑该行：

yline$x <- unit(rep(1, 4), "npc")
yline$y <- unit(c(0, 0.1, 1, 0.15), "npc")
yline$id <- c(1, 1, 2, 2)
yline$arrow <- arrow(angle = 90)

将其放回 gtable 对象并绘制它：

yaxis$children[[1]] <- yline

gt$grobs[[is_yaxis]] <- yaxis

# grid plotting syntax
grid.newpage(); grid.draw(gt)      

您可以在行编辑步骤中根据需要做出风格选择。