Need Help in Perl looping - perl

Question

I have a file with following data. I want to print in an external file with sum of every 9 rows. Here is my data.
file.xyz
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
My output looks like
-2.121332105 -5.405270886 -2.234333276 6.221675693
-2.121332105 -5.405270886 -2.234333276 6.221675693
Where the first line is sum of 1-9 and second line is sum from 10-18. Here data are same for first 9 and last 9 rows, it gives same value. I want to print sum of EVERY NINE lines of big files with thousands line file.
Here is my code, it calculates the total sum, but I need to split into two parts as above.
Thank you for your help and appreciated.
my #sums;
open FILE, "file.xyz" or die "Can't find";
while( <FILE> ) { # there is FILE written within angular brackets
my #summands = split / /;
foreach my $i ( 0 .. $#summands ) {
$sums[$i] += $summands[$i];
}
}
$total = sqrt($sums[0]*$sums[0]+$sums[1]*$sums[1]+$sums[2]*$sums[2]);
print "$sums[0], $sums[1], $sums[2], $total\n";

Answer 1

Something like the following:
use strict;
use warnings;
use autodie;
open my $fh, '<', 'file.xyz';
my #sums;
my $n = 0;
while (<$fh>) {
my #summands = split /\s+/;
foreach my $i ( 0 .. $#summands ) {
$sums[$i] += $summands[$i];
}
unless ( ++$n % 9 ) {
my $total = sqrt( $sums[0] * $sums[0] + $sums[1] * $sums[1] + $sums[2] * $sums[2] );
print "$sums[0], $sums[1], $sums[2], $total\n";
#sums = ();
}
}

Answer 2

Add a line counter and move the $total and print code into the loop under a conditional. You'll also need to clear the sums there.
if ($lines % 9 == 0) {
...
}

Answer 3

Use Input line number, $., to determine when your on every 9th line:
use strict;
use warnings;
use autodie;
use List::Util qw(sum);
#open my $fh, '<', "file.xyz";
my $fh = \*DATA;
my #sums;
while (<$fh>) {
my #cols = split ' ';
for my $i ( 0 .. $#cols ) {
$sums[$i] += $cols[$i];
}
if ( ( $. % 9 ) == 0 or eof ) {
my $weighted_total = sqrt sum map $_**2, #sums;
print join( ', ', #sums, $weighted_total ), "\n";
#sums = ();
}
}
warn "FH did not end an on even multiple of 9" if $. % 9;
__DATA__
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
-0.485718003092488 3.25568455554021 -0.60544991716881
-1.01253068155602 -2.49251542491767 0.713923699625837
0.791137982988487 -2.56492609246597 -0.853251541212567
Outputs:
-2.12133210498006, -5.40527088553029, -2.23433327626662, 6.22167569349391
-2.12133210498006, -5.40527088553029, -2.23433327626662, 6.22167569349391

Answer 4

The whole thing in Perl-golf style, watered down with a bit of whitespace and indentation:
while (<>) {
#l = split;
#s = map { $s[$_] + $l[$_] } 0..$#l;
next if ++$n % 9;
$, = ' ';
print #s, sqrt(eval join '+', (map { $_*$_ } #s)), "\n";
#s = ();
}
And some real Perl-golf, inspired by #Nemo, but even shorter:
perl -lanE '$s[$_]+=$F[$_]for 0..$#F;$.%9&&next;print"#s #{[sqrt eval join qq(+),map $_**2,#s]}";#s=()'
Finding the used tricks is left as an exercise to the readers. :-)