Save a zip file with the data used to create each plot.

save_plot_data.R

# Define the directory where to save the plot data
knitr::opts_chunk$set(plot_data_dir = "plot-data2")

save_plot_data <- function(plot, label = "plot", dir = NULL) {
  # If the user didn't set up a dir explicitly, don't do anything
  if (is.null(dir)) {
    return(invisible(NULL))
  }
  
  if (!dir.exists(dir)) {
    dir.create(dir)
  }
  
  # Build the ggplot2 plot. 
  gg <- ggplot2::ggplot_build(plot)
  
  # Get the data of each layer into a list.
  datas <- gg[["data"]]
  
  # Get the name of the geom in each layer
  geom_names <- vapply(gg[["plot"]][["layers"]], 
                       function(x) class(x[["geom"]])[1], 
                       FUN.VALUE = character(1)
  )
  geom_names <- make.unique(geom_names, sep = "_")
  
  # Save the data of each label into its own file and 
  # zip them. 
  temp <- tempdir(TRUE)
  files <- vapply(seq_along(datas), 
                  function(l) {
                    file <- file.path(temp, paste0(geom_names[l], ".csv"))
                    write.csv(datas[[l]], file, row.names = FALSE)
                    file  
                  }, 
                  FUN.VALUE = character(1)
  )
  
  zipfile <- file.path(dir, paste0(label, ".zip"))
  if (file.exists(zipfile)) {
    file.remove(zipfile)   # Need to remove previous versions of the data
  }
  zip(zipfile, 
      files = files, 
      flags = "-r9Xj"  # To "flatten" the files
  ) 
  return(invisible(NULL))
}

# Create the print method and register it. 
# From https://bookdown.org/yihui/rmarkdown-cookbook/opts-render.html
knitr_print.gg <- function(x, options, ...) {
  save_plot_data(x, options$label, options$plot_data_dir)
  NextMethod("knitr_print")
}

registerS3method(
  "knit_print", "gg", knitr_print.gg,
  envir = asNamespace("knitr")
)