使用ggnewscale包创建多个比例尺时，如何更改图例标题位置？

Question

我创建了一个使用ggnewscale软件包创建的具有2个颜色比例和2个线型比例的打印。我希望图例显示在绘图的底部，图例标题显示在标签的上方。我半途而废，因为在我的尝试中，第一个音阶(来自geom_vline())没有以我想要的方式出现。在用new_scale()和new_scale_color().Does声明下一个比例之前，我甚至试图指出这个比例的理想位置，有人知道我如何解决这个问题吗？

library(ggplot2)
library(ggnewscale)

mtcars$cyl <- factor(mtcars$cyl)

# Attempt 1

ggplot(data = mtcars,
       aes(x = wt,
           y = mpg)) +
  geom_vline(aes(xintercept = gear,
                 color = "Important line",
                 linetype = "Important line")) +
  scale_linetype_manual(name = "Important lines",
                        values = 1) +
  scale_color_manual(name = "Important lines",
                     values = "red") +
  new_scale("linetype") +
  new_scale_color() +
  geom_line(aes(linetype = cyl,
                color = cyl)) +
  theme(legend.position = "bottom") +
  guides(linetype = guide_legend(title.position = "top"),
         color = guide_legend(title.position = "top"))

# Attempt 2

ggplot(data = mtcars,
       aes(x = wt,
           y = mpg)) +
  geom_vline(aes(xintercept = gear,
                 color = "Important line",
                 linetype = "Important line")) +
  scale_linetype_manual(name = "Important lines",
                        values = 1) +
  scale_color_manual(name = "Important lines",
                     values = "red") +
  guides(linetype = guide_legend(title.position = "top",
                                 label.position = "bottom"), # Before new scales
         color = guide_legend(title.position = "top",
                              label.position = "bottom")) +
  new_scale("linetype") +
  new_scale_color() +
  geom_line(aes(linetype = cyl,
                color = cyl)) +
  theme(legend.position = "bottom") +
  guides(linetype = guide_legend(title.position = "top"),
         color = guide_legend(title.position = "top"))

两次尝试都会产生相同的情节，这不是我想要的。

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Answer 1

不确定是否还有其他选择，但在使用ggnewscale时，对我起作用的是通过scale的guide参数设置指南的样式。为了实现这一点，我添加了一个´scale_color_discrete`：

library(ggplot2)
library(ggnewscale)

mtcars$cyl <- factor(mtcars$cyl)

ggplot(data = mtcars,
       aes(x = wt,
           y = mpg)) +
  geom_vline(aes(xintercept = gear,
                 color = "Important line",
                 linetype = "Important line")) +
  scale_linetype_manual(name = "Important lines",
                        values = 1, guide = guide_legend(title.position = "top") ) +
  scale_color_manual(name = "Important lines",
                     values = "red", guide = guide_legend(title.position = "top")) +
  new_scale("linetype") +
  new_scale_color() +
  geom_line(aes(linetype = cyl,
                color = cyl)) +
  scale_color_discrete(guide = guide_legend(title.position = "top")) +
  theme(legend.position = "bottom")

​

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