title: Drawing a heatmap in R based on zipcodes only
body: <p>I want to draw a heatmap in R but my datafile is like this</p>
  
  <pre><code>Lat, Long, Zip, Zvalue
  </code></pre>
  
  <p>I basically need to interpolate between lat and long values and draw colors based on the zvalue</p>
  
  <p>How can I do that in R</p>
  
  <p>I eventually want to get something like this</p>
  
  <p><img src="https://i.stack.imgur.com/KcKyF.jpg" alt="enter image description here"></p>