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adding array elements

by Sidac (Initiate)
on Mar 09, 2011 at 14:15 UTC ( #892197=perlquestion: print w/replies, xml ) Need Help??
Sidac has asked for the wisdom of the Perl Monks concerning the following question:

Hello, i have a text file with numbers arranged as groups seperated by blank(empty) lines such as -
_DATA_ 20.187 15.415 8.663 6.001 6.565 6.459 6.564 13.454 13.475 13.220 +12.982 13.502 13.774 13.490 19.715 14.726 8.307 5.833 6.367 6.089 6.444 6.403 8.672 8.236 +12.982 13.502 13.774 13.490 20.099 15.205 8.763 6.317 6.861 6.973 6.701 6.334 8.406 8.155 + 7.395 8.156 9.551 8.530
How can i add all the first elements (20.187+19.715+20.099 etc ) , second elements (15.415+14.726+15.205) and so on in the list.(Groups are always of equal length. thanks

Replies are listed 'Best First'.
Re: adding array elements
by johngg (Abbot) on Mar 09, 2011 at 14:56 UTC

    Have a look at $INPUT_RECORD_SEPARATOR or $/ in perlvar for how to read your data file record by record. Have a look at split to break each record into fields and perldsc and push for building an array of arrays. Then think how you would iterate over all of the elements; perhaps a nested loop?

    Have a go at putting this all together then come back to the Monastery with any problems you are having with your code.

    Cheers,

    JohnGG

Re: adding array elements
by JavaFan (Canon) on Mar 09, 2011 at 14:44 UTC
    use 5.010; my @s; while (<DATA>) { my @e = split; $s[$_] += $e[$_] for 0 .. $#e; } say "@s";

      You could also add up the elements on each line with sum from List::Util, so the code above would become:

      use 5.010; use List::Util qw(sum); my @s; push @s, sum( split ) while <DATA> say "@s";
        Yeah, and I guess one could dance around in the streets as well.

        Considering that you are presenting a solution for a problem that isn't the OPs, what exactly is your point?

Re: adding array elements
by Anonymous Monk on Mar 09, 2011 at 14:44 UTC
    Read perlintro, read from data, split, iterate, add ... actually, you know what, considering your first question, subtraction in array, how about you ask that guy?
Re: adding array elements
by Fletch (Chancellor) on Mar 09, 2011 at 17:03 UTC
    ;; Presented with just about as much Perl as the OP . . . (ns sumcols (:use [clojure.contrib.str-utils :only (re-split)]) (:use [clojure.contrib.duck-streams :only (read-lines)])) (defn sumline [acc line] (loop [a acc l (map #(Float. %) (re-split #"\s+" line)) idx 0] (if (empty? l) a (recur (assoc a idx (+ (get a idx 0) (first l))) (rest l) (inc i +dx))))) (defn sumcols [filename] (loop [acc {} lines (filter #(> (count %) 0) (read-lines filename))] (if (empty? lines) (vals acc) (recur (sumline acc (first lines)) (rest lines))))) (println (sumcols (first *command-line-args*)))

    The cake is a lie.
    The cake is a lie.
    The cake is a lie.

Re: adding array elements
by Neighbour (Friar) on Mar 09, 2011 at 14:45 UTC
    You could do this by maintaining an array in which you keep incrementing the various fields as you read lines. Like so:
    use strict; my @data; open(INPUT,'<',"monks.dat") or die("Can't open file"); while (<INPUT>) { chomp; my @newdata = split(/ +/); for my $index (0 .. $#newdata) { $data[$index] += $newdata[$index]; } } close(INPUT);
    Though this does not check whether the amount of fields is actually the same or not :)
Re: adding array elements
by Gulliver (Monk) on Mar 09, 2011 at 17:19 UTC

    Why not use a spreadsheet? Import the data as fixed width or specify a space as the delimiter. Are you doing this to learn Perl?

    By the way: __DATA__ needs to have 2 underscores in front and back to work in a perl script, it looks like you only have one.

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