title: Plotting Separate Colors for Categorical Variable
body: <p>I am plotting quantity of a product bought versus household income. For each product bought I have a 'FALSE, TRUE' variable that indicates whether a coupon was used. I would like to change my plot so that if a coupon was used the plot will be green. How do I go about doing this? This should be simple but I can't figure it out. Thanks!</p>
  
  <pre><code>plot(quantity ~ household_income, data=blank, pch=19, col="blue",
       xlab="Household Income", ylab="Quantity Bought", col=2[usecoupon[TRUE]])
  </code></pre>