title: Is there a faster lm function
body: <p>I would like to get the slope of a linear regression fit for 1M separate data sets (1M * 50 rows for data.frame, or 1M * 50 for array). Now I am using the <code>lm()</code> function, which takes a very long time (about 10 min). </p>
  
  <p>Is there any faster function for linear regression?</p>