e2pdf / vendors / svggraph / BestFitLine.php

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1	<?php
2	/**
3	* Copyright (C) 2020 Graham Breach
4	*
5	* This program is free software: you can redistribute it and/or modify
6	* it under the terms of the GNU Lesser General Public License as published by
7	* the Free Software Foundation, either version 3 of the License, or
8	* (at your option) any later version.
9	*
10	* This program is distributed in the hope that it will be useful,
11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13	* GNU Lesser General Public License for more details.
14	*
15	* You should have received a copy of the GNU Lesser General Public License
16	* along with this program. If not, see <http://www.gnu.org/licenses/>.
17	*/
18	/**
19	* For more information, please contact <graham@goat1000.com>
20	*/
21
22	namespace Goat1000\SVGGraph;
23
24	/**
25	* Class for calculating a best-fit line
26	*/
27	class BestFitLine {
28
29	protected $graph;
30	protected $points;
31	protected $line;
32	protected $projection;
33
34	public function __construct(&$graph, $points)
35	{
36	$this->graph =& $graph;
37	$this->line = new PathData;
38	$this->projection = new PathData;
39	$this->points = $points;
40	}
41
42	/**
43	* Calculates the line and projection
44	*/
45	public function calculate(BoundingBox $area, $limit_start, $limit_end,
46	$project_start, $project_end)
47	{
48	// can't draw a line through fewer than 2 points
49	if(count($this->points) < 2)
50	return false;
51
52	$sum_x = $sum_y = $sum_x2 = $sum_xy = 0;
53	foreach($this->points as $p) {
54	$sum_x += $p->x;
55	$sum_y += $p->y;
56	$sum_x2 += pow($p->x, 2);
57	$sum_xy += $p->x * $p->y;
58	}
59
60	$mean_x = $sum_x / count($this->points);
61	$mean_y = $sum_y / count($this->points);
62
63	if($sum_x2 == $sum_x * $mean_x) {
64	// vertical line
65	$slope = null;
66	$y_int = $mean_x;
67	} else {
68	$slope = ($sum_xy - $sum_x * $mean_y) / ($sum_x2 - $sum_x * $mean_x);
69	$y_int = $mean_y - $slope * $mean_x;
70	}
71	$this->buildPaths($slope, $y_int, $area, $limit_start, $limit_end,
72	$project_start, $project_end);
73	}
74
75	/**
76	* Builds the line and projection paths.
77	* For vertical lines, $slope = null and $y_int = $x
78	*/
79	protected function buildPaths($slope, $y_int, $area, $limit_start, $limit_end,
80	$project_start, $project_end)
81	{
82	// initialize min and max points of line
83	$x_min = $limit_start === null ? 0 : max($limit_start, 0);
84	$x_max = $limit_end === null ? $area->width() : min($limit_end, $area->width());
85	$y_min = 0;
86	$y_max = $area->height();
87	$line = new PathData;
88	$projection = new PathData;
89
90	if($slope === null) {
91	// line is vertical!
92	$coords = [
93	'x1' => $y_int, 'x2' => $y_int,
94	'y1' => $y_min, 'y2' => $y_max
95	];
96	} else {
97	$coords = $this->boxLine($x_min, $x_max, $y_min, $y_max, $slope, $y_int);
98
99	if($project_end) {
100	$pcoords = $this->boxLine($coords['x2'], $area->width(), $y_min, $y_max,
101	$slope, $y_int);
102	if($pcoords !== null) {
103	$x1 = $pcoords['x1'] + $area->x1;
104	$x2 = $pcoords['x2'] + $area->x1;
105	$y1 = $area->y2 - $pcoords['y1'];
106	$y2 = $area->y2 - $pcoords['y2'];
107	$projection->add('M', $x1, $y1, 'L', $x2, $y2);
108	}
109	}
110	if($project_start) {
111	$pcoords = $this->boxLine(0, $coords['x1'], $y_min, $y_max,
112	$slope, $y_int);
113	if($pcoords !== null) {
114	$x1 = $pcoords['x1'] + $area->x1;
115	$x2 = $pcoords['x2'] + $area->x1;
116	$y1 = $area->y2 - $pcoords['y1'];
117	$y2 = $area->y2 - $pcoords['y2'];
118	$projection->add('M', $x1, $y1, 'L', $x2, $y2);
119	}
120	}
121	}
122	$x1 = $coords['x1'] + $area->x1;
123	$x2 = $coords['x2'] + $area->x1;
124	$y1 = $area->y2 - $coords['y1'];
125	$y2 = $area->y2 - $coords['y2'];
126	$line->add('M', $x1, $y1, 'L', $x2, $y2);
127
128	$this->projection = $projection;
129	$this->line = $line;
130	return true;
131	}
132
133	/**
134	* Returns the best-fit line as PathData
135	*/
136	public function getLine()
137	{
138	return $this->line;
139	}
140
141	/**
142	* Returns the projection line(s) as PathData
143	*/
144	public function getProjection()
145	{
146	return $this->projection;
147	}
148
149	/**
150	* Returns the coordinates of a line that passes through a box
151	*/
152	public static function boxLine($x_min, $x_max, $y_min, $y_max, $slope, $y_int)
153	{
154	$x1 = $x_min;
155	$y1 = $slope * $x1 + $y_int;
156	$x2 = $x_max;
157	$y2 = $slope * $x2 + $y_int;
158
159	if($slope != 0) {
160	if($y1 < 0) {
161	$x1 = -$y_int / $slope;
162	$y1 = $y_min;
163	} elseif($y1 > $y_max) {
164	$x1 = ($y_max - $y_int) / $slope;
165	$y1 = $y_max;
166	}
167
168	if($y2 < 0) {
169	$x2 = - $y_int / $slope;
170	$y2 = $y_min;
171	} elseif($y2 > $y_max) {
172	$x2 = ($y_max - $y_int) / $slope;
173	$y2 = $y_max;
174	}
175	}
176	if($x1 == $x2 && $y1 == $y2)
177	return null;
178	return compact('x1','y1','x2','y2');
179	}
180	}
181
182