Quick and dirty code illustrating the principle, undoubtedly fraught with syntax errors and incorrectly offset list indexes; 
@tables = ('csv_1', 'csv_2', ..., 'csv_n');
# or a directorylist to get all csv files in your directory

$num_types = 6;
$num_lengths = 9;

for $table (0 .. $#tables) {

     #parse file into 2-d list
     open(FILE, $tables[$table]);
     while($line = <FILE>) {
          @line_parts = split(/delimiter/, $line);
          push @this_table, [ @line_parts ];
     }
     close(FILE);

     #keep a running total of counts for each position
     for $length (1 .. $num_lengths) {
          for $type (1 .. $num_types) {
               $totals[$length][$type] = $totals[$length][$type] + $th
+is_table[$length-1][$type-1];
               $totals_squared[$length][$type] = $totals_squared[$leng
+th][$type] + ($this_table[$length-1][$type-1]^2);
          }
     }
}

#you now have everything you need to calcluate mena and sd for every p
+osition
for $i (0 .. $#totals) {
     for $j (0 .. $#{$totals[$i]}) { #check syntax!
          $mean = $totals[$i][$j]/$#tables;
          $sd = sqrt( ($totals_squared[$i][$j] -($totals[$i][$j]^s/$#t
+ables))/ ($#tables-1) )
          #note that this considers the data as a 'sample'.  
          #If it is to be considered a 'population', then replace "$#t
+ables-1" with $#tables
     }
}

[download]
For info on the raw score method of calculating sd, see
http://www.mnstate.edu/wasson/ed602calcsdraws.htm
or
http://www.med.umkc.edu/tlwbiostats/variability.html

In reply to Re: Mean and standard deviation amongst multiple matrices by punch_card_don
in thread Mean and standard deviation amongst multiple matrices by knirirr

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