Re^2: Performing Mathematical Operation on Specific Column of text File

Hi Aaron, I think this approach may be more complicated than it's worth. I think I am going to try another approach, in which I will loop through a list of files, extract the 9th column of times, sum the ninth column, provide a counter to count the number of lines in the column that match the conditions I need, then find the mean by taking the total(sum) and dividing by that counter. The logic is provided below:

 
    $total = 0;
    $count = 0;
 for ($j = 2; $j < @tableb; $j++) {
        chomp ($tableb[$j]);
        ($netsta,$delay_time) = (split /\s+/,$tableb[$j])[1,9];
        ($net,$sta) = (split /\./, $netsta)[0,1];
        if ($net eq "ZJ") {
            $count = $count + 1;
            $total = $total + $delay_time;
            $mean = $total/$count;
            print $mean, "\n";
        }
[download]

The for loop is looping through a file called $tableb, and if $net in the first column equals "ZJ", add to the counter, and then add the delay_time. Then I want to get the mean, and I output the mean. When printing out the mean, I get:

 
-0.9188
-1.0063
-0.585466666666667
-0.705775
-0.80838
-0.80595
-0.722071428571429
-0.6714
-0.773888888888889
-0.84067
-0.9097
-0.958375

-0.7386
-0.7877
-0.784433333333333
-0.69155
-0.78836
-0.779766666666667
-0.820314285714286
-0.8476
-0.802544444444444
-0.88008
-0.9104
-0.916916666666666
-0.962815384615385
-1.0093
[download]

where the LAST value before each line break (-0.958375 and -1.0093) are the means that I need -- they are the total means. Now the question I have is, how do I extract that last value, set it to a variable, and then later on, subtract it from the $delay_time when I need to print it out (which isn't provided here)? TLDR: When printing out the means, the means iteratively add up, and then I need to extract the final mean once the for loop is finished looping through each column. That final mean (the total mean) will then be sent to a variable to be used for subtraction purposes later. Does that make sense? I apologize if it's not clear. One option I found was using the -1 option to extract the last line of each output. Would that work?

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Re^3: Performing Mathematical Operation on Specific Column of text File by aaron_baugher (Curate) on May 16, 2015 at 02:07 UTC
I'm not clear on everything you're trying to do. But to your main question: how to save the last calculated mean so it can be used after the loop, just make sure you declare the variable outside the loop before it starts, like this: `my $mean; my $total = 0; my $count = 0; for ($j = 2; $j < @tableb; $j++) { # do other calcuations if(this_line_matches()){ $mean = $title/$count; # use $mean from outside the loop } } print $mean; # now contains the last value calculated inside the loop` [download] If you don't actually need to calculate the mean for each loop, you could move that calculation to after the loop and only do it once. Aaron B. Available for small or large Perl jobs and *nix system administration; see my home node.	[reply] [d/l]

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Re^3: Performing Mathematical Operation on Specific Column of text File
by aaron_baugher (Curate) on May 16, 2015 at 02:07 UTC

I'm not clear on everything you're trying to do. But to your main question: how to save the last calculated mean so it can be used after the loop, just make sure you declare the variable outside the loop before it starts, like this:

my $mean;
my $total = 0;
my $count = 0;
for ($j = 2; $j < @tableb; $j++) {
  # do other calcuations
  if(this_line_matches()){
    $mean = $title/$count;  # use $mean from outside the loop
  }
}
print $mean; # now contains the last value calculated inside the loop
[download]

If you don't actually need to calculate the mean for each loop, you could move that calculation to after the loop and only do it once.

Aaron B.
Available for small or large Perl jobs and *nix system administration; see my home node.

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