CODEWITHSUNDEEP
regexarraysperlhashincrement
user2941526
user2941526

Reputation: 497

Perl: Looping Through an Array to Increment the Values of a Hash

I am new to perl and I have a problem that I'm trying to solve. At this stage in my program, I have placed a file into an array and created a hash where all the keys are numbers, that increase by a user specified bin size, within a range The values of all keys are set to 0. My goal is to loop through the array and find numbers that match the keys of my hash, and increment the corresponding value by 1 in the event of a match. To make finding the specific value within the array a bit easier, each line of the array will only contain one number of interest, and this number will ALWAYS be a decimal, so maybe I can use the regex:

=~ m{(\d+\.\d+)}

to pick out the numbers of interest. After finding the number of interest, I need to round down the number (at the minute I an using "Math::Round 'nlowmult';") so that it can drop into the appropriate bin (if it exists), and if the bin does not exist, the loop needs to continue until all lines of the array have been scanned.

So the overall aim is to have a hash which has a record of the number of times that values in this array appear, within a user specified range and increment (bin size).

At the minute my code attempting this is (MathRound has been called earlier in the program):

my $msline;
foreach $msline (@msfile) {

    chomp $msline;
    my ($name, $pnum, $m2c, $charge, $missed, $sequence) = split (" ", $msline);

    if ($m2c =~ /[$lowerbound,$upperbound]/) {

        nlowmult ($binsize, $m2c);
        $hash{$m2c}++;

    }

}

NOTE: each line of the array contains 6 fields, with the number of interest always appearing in the third field "m2c".

The program isn't rounding the values down, neither is it adding values to the keys, it is making new keys and incrementing these. I also don't think using split is a good idea, since a real array will contain around 40,000 lines. This may make the hash population process really slow.

Where am I going wrong? Can anybody give me any tips as to how I can go about solving this problem? If any aspects of the problem needs explaining further, let me know!

Thank you in advance!

Upvotes: 1

Views: 1884

Answers (2)

Blake
Blake

Reputation: 11

I think the main problem is your line:

nlowmult ($binsize, $m2c);

Changing this line to:

$m2c = nlowmult ($binsize, $m2c);

would solve at least that problem, because nlowmult() doesn't actually modify $m2c. It just returns the rounded result. You need to tell perl to store that result back into $m2c.

You could combine that line and the one below it if you don't want to actually modify the contents of $m2c:

$hash{nlowmult ($binsize, $m2c)}++;

Probably not a compete answer, but I hope that helps.

Upvotes: 1

Barmar
Barmar

Reputation: 781726

Change:

if ($m2c =~ /[$lowerbound,$upperbound]/) {

    nlowmult ($binsize, $m2c);
    $hash{$m2c}++;

}

to:

if ($m2c >= $lowerbound && $m2c <= $upperbound) {

    $m2c = nlowmult ($binsize, $m2c);
    $hash{$m2c}++;

}

You can't use a regular expression like that to test numeric ranges. And you're using the original value of $m2c as the hash key, not the rounded value.

Upvotes: 1

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