How to save a plot as image on disk from Viewer in RStudio?

Question

Summary: my ultimate goal is to use rCharts , and specifically Highcharts , as part of a ReporteRs PowerPoint report automation workflow. One of the charts I would like to use is rendered as html in the Viewer pane in Rstudio, and addPlot(function() print(myChart)) does not add it to the PowerPoint. As a workaround, I decided to try to save myChart to disk, from where I could just add it to the PowerPoint that way.

So my question is really, How do I get my html image into my ReporteRs workflow? Either getting it saved to a disk, or getting it to be readable by ReporteRs would solve my problem.

This question is really the same as this one , but I'm using rCharts , specifically the example found here :

#if the packages are not already installed
install.packages('devtools')
require(devtools)
install_github('rCharts', 'ramnathv')

#code creates a radar chart using Highcharts
library(rCharts)
#create dummy dataframe with number ranging from 0 to 1
df<-data.frame(id=c("a","b","c","d","e"),val1=runif(5,0,1),val2=runif(5,0,1))
#muliply number by 100 to get percentage
df[,-1]<-df[,-1]*100

myChart <- Highcharts$new()
myChart$chart(polar = TRUE, type = "line",height=500)
myChart$xAxis(categories=df$id, tickmarkPlacement= 'on', lineWidth= 0)
myChart$yAxis(gridLineInterpolation= 'circle', lineWidth= 0, min= 0,max=100,endOnTick=T,tickInterval=10)
myChart$series(data = df[,"val1"],name = "Series 1", pointPlacement="on")
myChart$series(data = df[,"val2"],name = "Series 2", pointPlacement="on")
myChart

So if I try

> png(filename="~/Documents/name.png")
> plot(myChart)
Error in as.double(y) : 
  cannot coerce type 'S4' to vector of type 'double'
> dev.off()

I get that error.

I've looked into Highcharts documentation , as well as many other potential solutions that seem to rely on Javascript and phantomjs . If your answer relies on phantomjs , please assume I have no idea how to use it. webshot is another package I found which is even so kind as to include an install_phantomjs() function, but from what I could find, it requires you to turn your output into a Shiny object first.

My question is really a duplicate of this one , which is not a duplicate of this one because that is how to embed the html output in Rmarkdown, not save it as a file on the hard drive.

I also found this unanswered question which is also basically the same.

edit: as noted by @hrbrmstr and scores of others, radar charts are not always the best visualization tools. I find myself required to make one for this report.

Answer 1

The answer turned out to be in the webshot package. @hrbrmstr provided the following code, which would be run at the end of the code I posted in the question:

# If necessary
install.packages("webshot")
library(webshot)
install_phantomjs()

# Main code
myChart$save("/tmp/rcharts.html")
webshot::webshot("/tmp/rcharts.html", file="/tmp/out.png", delay=2)

This saves the plot to the folder as an html , and then takes a picture of it, which is saved as a png .

I can then run the ReporteRs workflow by using addImage(mydoc, "/tmp/out.png") .