in reply to Calculate log of matrix values

The log function is not defined for 0. You can check for zeros in the loop: 
$lnpam[$i][$j] = log $matrix[$i][$j] if $matrix[$i][$j];

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The resulting matrix would have undefined values in the corresponding places.

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Re^2: Calculate log of matrix values
by madM (Beadle) on Aug 09, 2013 at 14:08 UTC
    i solved the problem using this: 
    LINE: for (my $i=0; $i<20; $i++){
    for (my $j=0; $j<20; $j++){
        if ($matrix[$i][$j] =~ /[^0.00]/){
            $lnpam[$i][$j] = log $matrix[$i][$j];
        }else{ next LINE;
        }
    }
}

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    thanks a lot for the quick answer!
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[d/l]
      if ($matrix[$i][$j] =~ /[^0.00]/){

      This does not do what you think it does, but it is at least close. You are really only doing if ($matrix[$i][$j] =~ /[^0.]/){ IE: does the string have at least one character that is not a literal '0' or a '.'

      See: Bracketed Character Classes

      Why not make the test if ($matrix[$i][$j] > 0)? That's much simpler and faster, and will not fail on "-0.00 " or " 0.00" or regular negative numbers.

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[d/l]
[select]
        thanks! you are right :)
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