在 cowplot：：save_plot 中使用 base_height 自动为 stringr：：str_wrap 分配宽度

问：

我想自动分配值，以便文本适合绘图的宽度，当我知道我想在以下方面使用时：widthstr_wrapbase_heightsave_plot

library(ggplot2)
library(cowplot)
library(stringr)
caption_text <- c("this is a very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very long caption text")
p <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, colour = Species)) +
  geom_point() +
  theme(axis.text = element_text(size = 12, face = "bold", colour = "black"),
        axis.title = element_text(size = 16, face = "bold", colour = "black")) + 
  labs(x = "Length", y = "Width",
       caption = str_wrap(caption_text, width = 120))
p
save_plot("figures/pic.png",
          p,
          base_height = 8
          ) 

（文字与剧情宽度不符）

我希望能够做的是像这样自动化它：

my_base_height = 8
str_wrap_width = my_base_height*SOME_VALUE
p <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, colour = Species)) +
  geom_point() +
  theme(axis.text = element_text(size = 12, face = "bold", colour = "black"),
        axis.title = element_text(size = 16, face = "bold", colour = "black")) + 
  labs(x = "Length", y = "Width",
       caption = str_wrap(caption_text, str_wrap_width))
p
save_plot("figures/pic.png",
          p,
          base_height = my_base_height
)

但我不知道如何提取具有已知值（英寸）的绘图的宽度，以便将其提供给.cowplotbase_heightstr_wrap

有什么想法吗？ 谢谢