title: matlab: keeping only first N digits of numbers
body: <p>I am trying to find a way in Matlab to truncate values of a vector, keeping only the first N digits (I don't want to round it, just to cut it.) of them. I wrote something which converts the values in strings, cut those and returns the number truncated, but it is too slow. </p>
  
  <p>Any more clever solution?</p>
  
  <p>Thanks a lot in advance!</p>