Issues with the export_png() function on Linux, please help!

[Wario84]

Hi guys,

Hope that you can help me out. I have invested quite some time tryinng to set up the export function, both Linux and Windows, without success. I will post the procedure that I followed.

Installation of node.js + vega

To instaI node.js in Linux, I followed the procedure suggested

1. Install Curl
   sudo apt-get install curl
2. Install node.js

curl -sL https://deb.nodesource.com/setup_4.x | sudo -E bash -
sudo apt-get install -y nodejs

1. Set the folder to install global packages
   npm config set prefix '~/npm'
2. Create a .bashrc file
   export PATH="$HOME/npm/bin:$PATH"
. ~/.bashrc
echo $PATH
3. Install Vega

sudo apt-get install libcairo2-dev
sudo apt-get install libjpeg-dev
sudo apt-get install libgif-dev
npm -g install vega

My R code

library(ggvis)
mtcars %>% ggvis(~mpg, ~hp) %>% layer_points() %>% export_png()
Writing to file plot.png
Error in vega_file(vis, file = file, type = "png") : 
Conversion program vg2pngnot found.

Any ideas how to solve this?

[Chris1221]

This is a bit of a work around, and hopefully you'll get help from someone who actually knows what they're talking about, but check out ggvis:::vega_file:

> ggvis:::vega_file
function (vis, file = NULL, type = "png") 
{
    if (!(type %in% c("png", "svg"))) 
        stop("type must be 'png' or 'svg'")
    if (is.null(file)) {
        file <- paste0("plot.", type)
        message("Writing to file ", file)
    }
    temp_dir <- tempfile(pattern = "ggvis")
    dir.create(temp_dir)
    cmd <- paste0("vg2", type)
    cmdsearch <- Sys.which(paste0(c("", "./bin/", "./node_modules/.bin/"), 
        cmd))
    found_idx <- which(nzchar(cmdsearch))
    if (length(found_idx) == 0) 
        stop("Conversion program ", cmd, "not found.")
    cmd <- cmdsearch[min(found_idx)]
    json_file <- file.path(temp_dir, "plot.json")
    vega_json <- save_spec(vis, json_file)
    on.exit(unlink(json_file))
    system2(cmd, args = c(json_file, file))
}
<environment: namespace:ggvis>

It's looking for vg2png in either the current directory or in ./nodemodules/bin.

As a work around, try to find the vg2png file on your computer (I installed vega from github so I just set the working directory to the base repo for vega) and set your working directory there.