第 1 章 R Markdown

1.1 设置选项钩子附上图片下载链接

通过设置选项钩子，可以在图片输出设备多于 1 个时候，提供图片的下载链接。

knitr::opts_hooks$set(dev = function(options){
  if (length(options$dev) > 1){
    x = paste0("[", options$dev, "](", knitr::fig_path(options$dev), ")",
               collapse = " | ")
    options$fig.cap = paste(options$fig.cap, x, sep = " ")
  }
  options
})

下图中，使用了 dev = c('png', 'pdf', "tiff", "svg") 等 4 种图像设备，由于 dev 选项钩子的存在，将自动在图注中添加图片的下载链接。

plot(1:10)

图 1.1: This is a plot. png | pdf | tiff | svg

图注也可以使用文本引用，不影响钩子的应用效果。

plot(1:10)

图 1.2: 使用选项钩子在图注中添加下载链接。 png | pdf

1.2 使用自定义图形设备

All possible devices supported by knitr are: “bmp”, “postscript”, “pdf”, “png”, “svg”, “jpeg”, “pictex”, “tiff”, “win.metafile”, “cairo_pdf”, “cairo_ps”, “quartz_pdf”, “quartz_png”, “quartz_jpeg”, “quartz_tiff”, “quartz_gif”, “quartz_psd”, “quartz_bmp”, “CairoJPEG”, “CairoPNG”, “CairoPS”, “CairoPDF”, “CairoSVG”, “CairoTIFF”, “Cairo_pdf”, “Cairo_png”, “Cairo_ps”, “Cairo_svg”, “svglite”, “ragg_png”, and “tikz”.

From: https://bookdown.org/yihui/rmarkdown-cookbook/graphical-device.html

是不是可以使用 ppt 设备呢？

library(export)

The dev option can also be the name of a function. If so, the function seems like function(file, width, height), which has been described at https://yihui.org/knitr/options/#plots.

Therefore, a new PPTX device can be defined as:

# a pptx device
pptx = function(file, width, height){
  export::graph2ppt(file = file, width = width, height = height)
}

Notably, if multiple devices are used, you may need to specify the fig.ext option. For example, dev = c('png', 'pdf', 'pptx'), fig.ext=c("png","pdf","pptx"). See https://yihui.org/knitr/demo/graphics/#a-note-on-custom-graphical-devices.

plot(1:10)

图 1.3: 使用选项钩子在图注中添加下载链接。 png | pdf | pptx