title: How to calculate a multi-variable formula from a table of data
body: <p>I have a table of several independent variables that I need to calculate a formula from to generate the dependent variable. Though trial I have come up with a value for the dependent variable. 
  For example, I have a table like this:</p>
  
  <pre><code>x1 | x2 | x3 || z(value found by experiment)
  -------------------
  1  | 2  | 3  || 10
  3  | 4  | 5  || 14
  2  | 3  | 3  || 15
  1  | 2  | 7  || 9
  </code></pre>
  
  <p>now I want a formula such that:</p>
  
  <pre><code>f(x1,x2,x3) = z
  </code></pre>
  
  <p>Now how do I go through and get the value? Can you point me to some resources?</p>
  
  <p>I feel like I should remember this from my school days, but I dont.</p>
  
  <p><strong>Also:</strong> Do you know any tools that will do this for me? I have excel, but I cannot figure out how to do regression with more than one variable.</p>