viz.js.R

library(V8)
stopifnot(packageVersion("V8") >= "0.5")

# Create V8 context and load viz.js
ct <- new_context("window")
invisible(ct$source('http://mdaines.github.io/viz.js/viz.js'))

# This runs: Viz("digraph { a -> b; }", "svg")
svg <- ct$call("Viz", "digraph { a -> b; }", "svg")
cat(svg)

# View SVG in Rstudio:
tmp <- tempfile(fileext=".svg")
writeLines(svg, tmp)
rstudio::viewer(tmp)

Thanks for putting this up. Since DiagrammeR is installed, we could actually just use the local version of viz.js, so system.file(...).

Yes within a package you should preferably ship the js files in your inst dir (if copyright permits) and load them with system.file.