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#!/Users/colincrain/perl5/perlbrew/perls/perl-5.32.0/bin/perl
#
# white-line-fever.pl
#
# Line of Best Fit
# Submitted by: Ryan J Thompson
# When you have a scatter plot of points, a line of best fit is the
# line that best describes the relationship between the points, and
# is very useful in statistics. Otherwise known as linear
# regression.
#
# The method most often used is known as the least squares method,
# as it is straightforward and efficient, but you may use any
# method that generates the correct result.
#
# Calculate the line of best fit for the following 48 points:
#
# 333,129 39,189 140,156 292,134 393,52 160,166 362,122 13,193
# 341,104 320,113 109,177 203,152 343,100 225,110 23,186 282,102
# 284,98 205,133 297,114 292,126 339,112 327,79 253,136 61,169
# 128,176 346,72 316,103 124,162 65,181 159,137 212,116 337,86
# 215,136 153,137 390,104 100,180 76,188 77,181 69,195 92,186
# 275,96 250,147 34,174 213,134 186,129 189,154 361,82 363,89
#
# © 2022 colin crain
## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ##
use warnings;
use strict;
use utf8;
use feature ":5.26";
use feature qw(signatures);
no warnings 'experimental::signatures';
## SVG package
package SVG;
use Moo;
use feature qw(signatures);
no warnings 'experimental::signatures';
{
has groups => (
is => 'rw' ,
default => sub { return [] } );
has height => ( is => 'rw' );
has width => ( is => 'rw' );
around BUILDARGS => sub {
my ( $orig, $class, @args ) = @_;
return { height => $args[0],
width => $args[1] };
};
sub group( $self, $id, $attr ) {
push $self->groups->@*, [$id, $attr, []]
}
sub add( $self, $item ){
push $self->groups->[-1]->[2]->@*, $item;
}
## supported object primitives
sub circle( $self, $x, $y, $r=3) {
## default radius 3 for single point
return qq(<circle cx="${x}" cy="${y}" r="${r}" />);
}
sub line( $self, $x1, $y1, $x2, $y2 ) {
return qq(<line x1="${x1}" x2="${x2}" y1="${y1}" y2="${y2}" />);
}
## output
sub make_SVG( $self ) {
my $h = $self->height;
my $w = $self->width;
my $xml = <<~XML;
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
<svg height="${h}" width="${w}"
xmlns="http://www.w3.org/2000/svg"
xmlns:svg="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink">
XML
for my $g ( $self->groups->@* ){
my $tag = qq(<g id="$g->[0]" );
$tag .= qq($_="$g->[1]->{$_}" ).' ' for keys $g->[1]->%*;
$tag .= qq(>\n);
$tag .= qq( $_\n) for $g->[2]->@*;
$tag .= qq(</g>\n);
$xml .= $tag;
}
$xml .= qq(</svg>\n);
return $xml;
}
}
##/SVG
package main;
## input data
my @data = (
[333,129], [39,189], [140,156], [292,134], [393,52],
[160,166], [362,122], [13,193], [341,104], [320,113],
[109,177], [203,152], [343,100], [225,110], [23,186],
[282,102], [284,98], [205,133], [297,114], [292,126],
[339,112], [327,79], [253,136], [61,169], [128,176],
[346,72], [316,103], [124,162], [65,181], [159,137],
[212,116], [337,86], [215,136], [153,137], [390,104],
[100,180], [76,188], [77,181], [69,195], [92,186],
[275,96], [250,147], [34,174], [213,134], [186,129],
[189,154], [361,82], [363,89] );
## make SVG format data string
my $attr;
my $svg = new SVG(400,400);
$attr = { "fill"=>"blue" };
$svg->group( "points", $attr);
$svg->add( $svg->circle($_->@*) ) for @data;
$attr = { "stroke" => "red", "stroke-width" => "4" };
$svg->group( "best-fit-line", $attr );
$svg->add( $svg->line( best_fit(@data) ) );
## write to file, ./best-fit.svg
open my $fh, ">", "best-fit.svg" or die "cant open bestfit.svg to output: $!\n";
my $xml = $svg->make_SVG;
say $fh $xml;
close $fh;
sub best_fit (@points) {
my ($xsum, $ysum, $sqsum, $xysum);
for (@data) {
$xsum += $_->[0];
$ysum += $_->[1];
$sqsum += $_->[0] ** 2;
$xysum += $_->[0] * $_->[1];
}
my $slope = ((@data * $xysum) - ($xsum * $ysum)) / ((@data * $sqsum) - ($xsum ** 2));
my $intercept = ($ysum - ($slope * $xsum)) / @data;
## hardwired 400px canvas for now
my $xmax = 400;
## x1, y1, x2, y2
return (0, $intercept, 400, ($slope * 400 + $intercept))
}
=cut
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
<svg height="400" width="400"
xmlns="http://www.w3.org/2000/svg"
xmlns:svg="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink">
<g id="points" fill="blue" >
<circle cx="333" cy="129" r="3" />
<circle cx="39" cy="189" r="3" />
<circle cx="140" cy="156" r="3" />
<circle cx="292" cy="134" r="3" />
<circle cx="393" cy="52" r="3" />
<circle cx="160" cy="166" r="3" />
<circle cx="362" cy="122" r="3" />
<circle cx="13" cy="193" r="3" />
<circle cx="341" cy="104" r="3" />
<circle cx="320" cy="113" r="3" />
<circle cx="109" cy="177" r="3" />
<circle cx="203" cy="152" r="3" />
<circle cx="343" cy="100" r="3" />
<circle cx="225" cy="110" r="3" />
<circle cx="23" cy="186" r="3" />
<circle cx="282" cy="102" r="3" />
<circle cx="284" cy="98" r="3" />
<circle cx="205" cy="133" r="3" />
<circle cx="297" cy="114" r="3" />
<circle cx="292" cy="126" r="3" />
<circle cx="339" cy="112" r="3" />
<circle cx="327" cy="79" r="3" />
<circle cx="253" cy="136" r="3" />
<circle cx="61" cy="169" r="3" />
<circle cx="128" cy="176" r="3" />
<circle cx="346" cy="72" r="3" />
<circle cx="316" cy="103" r="3" />
<circle cx="124" cy="162" r="3" />
<circle cx="65" cy="181" r="3" />
<circle cx="159" cy="137" r="3" />
<circle cx="212" cy="116" r="3" />
<circle cx="337" cy="86" r="3" />
<circle cx="215" cy="136" r="3" />
<circle cx="153" cy="137" r="3" />
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