Aptech » Answers for "How can I extract specific rows based upon a logical expression?" http://www.aptech.com Fri, 08 Feb 2013 19:12:28 +0000 en-US hourly 1 http://wordpress.org/?v=3.4.1 By: aptech http://www.aptech.com/questions/how-can-i-extract-specific-rows-based-upon-a-logical-expression/#answer-1863 http://www.aptech.com/questions/how-can-i-extract-specific-rows-based-upon-a-logical-expression/#answer-1863#comments Mon, 08 Oct 2012 13:50:20 +0000 aptech http://www.aptech.com/questions/how-can-i-extract-specific-rows-based-upon-a-logical-expression/#answer-1863 Continue reading →]]> The GAUSS function selif will extract rows from a matrix that match a logical expression. For example:

x = { 1 3,
     -2 4,
      2 1,
      7 -9 };

mask = x[.,1] .> 0;
xout = selif(x, mask);

After the code above the variables will have the following values:

x = 
       1        3 
      -2        4 
       2        1 
       7       -9 
mask = 
       1 
       0 
       1 
       1 
xout = 
       1        3 
       2        1 
       7       -9
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