为什么在chartJSRadar（）之后调用legend（）导致“ plot.new尚未被调用”

Question

The context here is the R Project for Statistical Computing

Consider the following code (from chartJSRadar documentation)

library(radar chart)
labs <- c("Communicator", "Data Wangler", "Programmer",
      "Technologist",  "Modeller", "Visualizer")

scores <- list(
  "Rich" = c(9, 7, 4, 5, 3, 7),
  "Andy" = c(7, 6, 6, 2, 6, 9),
  "Aimee" = c(6, 5, 8, 4, 7, 6)
)

chartJSRadar(scores = scores, labs = labs, maxScale = 10)

I want to put a legend on in using:

legend("topleft", c("Rich","Andy","Aimee"), cex=0.8, fill=colors)

But I get the following error:

Error in strwidth(legend, units = "user", cex = cex, font = text.font) : 
  plot.new has not been called yet

I've seen many other questions about this error message. Some of them was because legend coordinates were off the chart. Some others give a workaround but do not explain why the error occur.

My question is: why am I getting this error? It seems something fundamentally wrong like an incompatibility between legend() and chartJSRadar(), but I don't get it.

Please advise!

Answer 1

If using R Studio make sure to run the entire chunk (not ctr + enter). I had a similar issue using igraph. I tried to attach the legend to the graph but had the same error message. Running the entire chunk worked.

Answer 2

It seems chartJSRadar does not call a plot but shows an interactive plot in the viewer. Hence a plot is not called and you cannot use legend() . From the documentation for chartJSRadar , it does seem like there is a legend option for the radar plot, see http://www.chartjs.org/docs/#radar-chart-chart-options :

//String - A legend template
legendTemplate : "<ul class=\"<%=name.toLowerCase()%>-legend\"><% for (var i=0; i<datasets.length; i++){%><li><span style=\"background-color:<%=datasets[i].strokeColor%>\"></span><%if(datasets[i].label){%><%=datasets[i].label%><%}%></li><%}%></ul>"

This is JavaScript, which I have no expertise in, so unfortunately this is as far as I can help you.

Answer 3

Try using fmsb package which has radarchart() function. You can plot the same for your data.

http://127.0.0.1:25882/library/fmsb/html/radarchart.html

I tried it in R and it works in R plot window. As I do not understand the radar chart data. You would definitely be able to do it with legend using radarchart() and legend() using package fmsb