title: How to I resize the outline of a pch plot point in base R?
body: <p>I'm tinkering with cex options in base R plots to resize my plot for a presentation slide.  I seem to be able to tweak most size aspects, but I notice the outline color of my pch point is not getting any bolder/thicker when the plot point becomes larger.  So the larger the plot point, the less noticeable the outline color.</p>
  
  <p>Found many websites (&amp; SO posts) on various cex options (cex, cex.main, cex.sub, cex.axis, cex.lab), but none seem to be adjusting the pch plot point.</p>
  
  <p>I'm aware that only certain pch symbols (21 to 25) can be used with fill color and outline.  My sample code uses 21 (circle).</p>
  
  <pre><code>data("mtcars")  # test data
  summary(mtcars[c("hp","mpg")]) # to find on min &amp; max values to set plot limits
  
  # set general features used for multiple plots
  par(bg="blue", fg="red", col="yellow", col.axis="white", col.lab="white", bty="n", cex=1.5)
  
  # test plot to illustrate, cex used here to further adjust plot points from par setting
  plot(mtcars$hp, mtcars$mpg, ylim=c(10, 35), xlim=c(50, 340), pch=21, bg="red", cex=2) 
  </code></pre>
  
  <p>Am I missing something about cex or is there a different solution without turning to ggplot?  I'm not adverse to ggplot if there is an option, but I'd like to see if it can be done in base R.</p>