title: Make a 2D pixel plot with matplotlib
body: <p>I got the following data from some calculations:</p>
  
  <pre><code>x, y, temp
  </code></pre>
  
  <p>where x and y are the coordinates of  a point in a 2D box of dimensions 10x10. Spacing is equal to 0.1. So there are 10000 different points and the resulting file looks like:</p>
  
  <pre><code>0.0 0.0 5.6
  0.1 0.0 3.2
  0.2 0.0 4.1
  ...
  9.9 9.9 2.1
  </code></pre>
  
  <p>I would like to prepare kind of a 2D plot with matplotlib, with 100x100 pixels, where each pixel gets a colour (rainbow colors going from red to violet, from the minimum to the maximum values of the third column) according to the value of the 3rd column, and data is read from this file. I wonder what is the best approach for this with matplotlib</p>