title: Heat map or density map in R
body: <p>I am new to R and trying to create a heat map or density map to show my results. I have x data for 20 different locations and for 20 years. I am trying to show differences in locations as well as in years in the same map. my data looks like this.</p>
  
  <pre><code>    1975    1977    1979    1981    1983    1985    1987    1989
  Dallas  25  28  27  29  31  33  35  37
  Houston 33  38  43  48  53  58  63  68
  Lubbock 28  29  31  33  35  37  39  41
  Austin  22  24  26  28  30  32  34  36
  San Antonio 31  32  33  34  35  36  37  38
  </code></pre>
  
  <p>Thank you for your help.</p>