如何让ggside中轴标题与图例相对主图居中对齐？

背景 #

我正在使用ggside包将数据的等高线图与折线图绘制在同一幅图中，绘图功能正常，但x、y轴标题及图例的位置存在问题——这些元素（如图中黑线所示）相对于整个绘图区域（主图+侧边图）居中，而非相对主图对齐。

初始绘图代码：

rm(list = ls(all = TRUE))

if (!require("ggplot2")) install.packages("ggplot2")
if (!require("ggside")) install.packages("ggside")

# 获取数据

# 等高线数据
set.seed(230529)

z <- runif(n = 100, min = -5, max = 20)
x <- y <- seq(1, length(z)/10, 1)
tmp <- expand.grid(x, y)
x <- tmp[,1]
y <- tmp[,2]

df.1 <- data.frame(x, y)
df.1$z <- z
df.1$level <- as.numeric(df.1$z)

# 折线图数据
y <- runif(n = length(z)/10, min = -5, max = 20)
x <- seq(1, length(y), 1)

df.2 <- data.frame(x = x, y = y)

# 绘图
ggplot(df.1, aes(x = x, y = y)) +
  geom_contour(aes(z = z, color = after_stat(level))) + 
  geom_hline(yintercept = sum(range(x))/2) +
  geom_vline(xintercept = sum(range(x))/2) +
  theme(aspect.ratio = 1) +
  geom_xsideline(data = df.2, aes(x = x, y = y)) +
  geom_ysideline(data = df.2, aes(x = y, y = x), orientation = "y")

初始问题 #

ggside是否有选项可将轴标题、图例这类元素相对主图对齐？若没有，能否通过hjust等参数自动调整位置？

已尝试的解决方法（更新） #

通过设置ggside.panel.scale，结合hjust和vjust参数可实现需求：

rm(list = ls(all = TRUE))

if (!require("ggplot2")) install.packages("ggplot2")
if (!require("ggside")) install.packages("ggside")

# 获取数据

# 等高线数据
set.seed(230529)

z <- runif(n = 100, min = -5, max = 20)
x <- y <- seq(1, length(z)/10, 1)
tmp <- expand.grid(x, y)
x <- tmp[,1]
y <- tmp[,2]

df.1 <- data.frame(x, y)
df.1$z <- z
df.1$level <- as.numeric(df.1$z)

# 折线图数据
y <- runif(n = length(z)/10, min = -5, max = 20)
x <- seq(1, length(y), 1)

df.2 <- data.frame(x = x, y = y)

# 绘图
ggplot(df.1, aes(x = x, y = y)) +
  geom_contour(aes(z = z, color = after_stat(level))) + 
  geom_hline(yintercept = sum(range(x))/2) +
  geom_vline(xintercept = sum(range(x))/2) +
  theme(axis.title.x = element_text(hjust = 0.4375),
        axis.title.y = element_text(vjust = 0.4375),
        legend.position = "right",
        legend.justification = c(1,0.4375),
        aspect.ratio = 1) +
  geom_xsideline(data = df.2, aes(x = x, y = y)) +
  geom_ysideline(data = df.2, aes(x = y, y = x), orientation = "y") +
  theme(ggside.panel.scale = 0.125,
        ggside.axis.text = element_blank(),
        ggside.axis.ticks = element_blank())

新问题 #

能否自动获取ggside.panel.scale的取值？

内容的提问来源于stack exchange，提问作者Excelsior