in reply to Working out frequency statistics with perl

You aren't showing the whole script, so I wonder... do you have these lines anywhere in your code (near the top)? 
use strict;
use warnings;

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Apart from that, I wonder if your "readmap" command ever outputs any lines with initial whitespace. If so, your split statement should be: 
    @fields = spit " ";

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because that will differ from /\s+/ -- try this snippet to see the difference: 
$_ = "   begins with whitespace";

@a = split " ";
@b = split /\s+/;

print "quoted-space split returns ", scalar @a, " elements\n";
print "\\s+ split returns ", scalar @b, ", first one has length ",leng
+th($b[0]),"\n";

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update: To clarify the issue, using "\s+" for splitting will get you into real trouble if the "readmap" output varies in terms of presence/absence of whitespace at the beginning of each line. If the output is consistent in this regard, then using "\s+" is probably not a problem -- you just need to make sure you've counted the field indexes correctly, so that $fields[2] etc really point at what you want them to point at.

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Re^2: Working out frequency statistics with perl
by wishartz (Beadle) on Jul 16, 2008 at 10:43 UTC
    Hello again Monks, thanks for everybody's feedback. To answer the last reply I got, I am using warnings and strict and I am not getting any errors. The output is always consistant as well. Here is a sample of the exact output, that from the readmap command if it matches the pattern StageTime.

    Read more... (22 kB)

    I don't understand the subroutine that was posted earlier. I don't understand what I am supposed to pass to items? Am I supposed to pass the sorted array, that is only the keys not the values? 
    
sub build_histogram {
   my ($bucket_size, @items) = @_;
   my %result;
   for (@items) {
       my $bucket = $bucket_size * floor($_ / $bucket_size);
       print "$bucket\n";
       $result{$bucket}++;
   }
   return %result;
}

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[d/l]
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      I don't understand the subroutine that was posted earlier. I don't understand what I am supposed to pass to items?

      A list of numbers from which you want to build your histogram. And it doesn't have to be sorted.

      Your sample data generates this histogram for me: 

      0: 67
30: 73
60: 93
90: 75
120: 26
150: 18
180: 10
210: 5
240: 2
270: 1
300: 1
330: 2
360: 1
390: 1
450: 1
840: 1

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[d/l]
        Please excuse my ignorance, but I'm not sure where to call the subroutine build histogram, and how to print out the returned result hash. I think I'm going about this in the wrong way. I tried this: 
        open(READMAP, "$command  |") || error_exit("Cannot run readmap, $!"); 
+#run the readmap command
while(<READMAP>) {    #loop through the output of the readmap command
        if (/StageTime/){
        @fields = split/\s+/;                                         
+  #Split the output by white space
        chop $fields[9];                                              
+  # Remove the period after the last digit
        $diskxStats[$i]{'filesize'}=$fields[2];
        $diskxStats[$i]{'ftptime'}=$fields[5];
        $diskxStats[$i]{'stagetime'}=$fields[9];
        if ( $fields[5] != 0 ){
        $diskxStats[$i]{'transferRate'} = $fields[2] / $fields[5];
        }
        else{
        $diskxStats[$i]{'transferRate'} = $fields[2];
        }
        if ( $fields[9] != 0 ){
        $diskxStats[$i]{'stagerate'} = $fields[2] / $fields[9];
        }
        else{
        $diskxStats[$i]{'stagerate'} = $fields[2];
        }
        $i++;
        }
}



for $i (0 .. $#diskxStats ) {
        build_histogram ($bin_stage, $diskxStats[$i]{'stagetime'});
        }

sub build_histogram {
   my ($bucket_size, @items) = @_;
   my %result;
   for (@items) {
       my $bucket = $bucket_size * floor($_ / $bucket_size);
  #     print "$bucket\n";
       $result{$bucket}++;
   }
   return %result;
}

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        Which is obviously incorrect, but not sure what I need to change to get the results you got?
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[d/l]

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