title: Why am I getting "plot.new has not been called yet" calling legend() after chartJSRadar()
body: <p>The context here is the R Project for Statistical Computing </p>
  
  <p>Consider the following code (from chartJSRadar documentation)</p>
  
  <pre><code>library(radar chart)
  labs &lt;- c("Communicator", "Data Wangler", "Programmer",
        "Technologist",  "Modeller", "Visualizer")
  
  scores &lt;- 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)
  </code></pre>
  
  <p>I want to put a legend on in using:</p>
  
  <pre><code>legend("topleft", c("Rich","Andy","Aimee"), cex=0.8, fill=colors)
  </code></pre>
  
  <p>But I get the following error:</p>
  
  <pre><code>Error in strwidth(legend, units = "user", cex = cex, font = text.font) : 
    plot.new has not been called yet
  </code></pre>
  
  <p>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.</p>
  
  <p>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. </p>
  
  <p>Please advise!</p>