Setup

library(tidyverse)
library(DiagrammeR)
library(DiagrammeRsvg)
library(magick)

DiagrammeR using grViz()

Define the graph:

g1 <- "digraph boxes_and_circles {
      graph [layout = circo,
             overlap = true]
      node [shape = circle,
            fixedsize = true,
            fontname = Helvetica,
            width = 1]
      Problem; Plan; Data; Analysis; Conclusion
    
      edge [color = grey]      
      Problem -> Plan
      Plan -> Data
      Data -> Analysis
      Analysis -> Conclusion
      Conclusion -> Problem
      }"

Print it to the screen:

grViz(g1)

This diagram is inspired by Figure 1 from the paper of Wild and Pfannkuch, 1999.

Export

Note that RStudio provides an Export button in the Viewer pane.

Convert to SVG, and export

SVG is an xml based markup language for defining 2D vector images see Wikipedia.

GraphViz can be described as follows:

Graphviz is open source graph visualization software. Graph visualization is a way of representing structural information as diagrams of abstract graphs and networks. It has important applications in networking, bioinformatics, software engineering, database and web design, machine learning, and in visual interfaces for other technical domains.

(taken from the link above)

We can convert from GraphViz to SVG using this function:

svg <- grViz(g1) %>% export_svg() 

Save this SVG markup as a text file, and your browser will display it.

fileConn<-file("graph.svg")
writeLines(svg, fileConn)
close(fileConn)

Convert SVG to PNG

There are a number of programs to convert from one image format to another. Image Magick is a popular tool (see this post for some discussion and problems).

Within R, one can call Image Magick, one can call IM using the magick package (see here).

img_svg <- image_read_svg('graph.svg', width = 400)
img_png <- image_convert(img_svg, "png")
image_write(img_png, path = "graph.png", format = "png")