Inizializzazione

jpgraph-3.5.0b1/src/Examples/fieldscatterex1.php

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+<?php // content="text/plain; charset=utf-8"
+require_once ('jpgraph/jpgraph.php');
+require_once ('jpgraph/jpgraph_scatter.php');
+
+$polex = 6;
+$poley = 40;
+
+function FldCallback($x,$y,$a) {
+    GLOBAL $polex, $poley;
+    $maxr = 3000;
+
+    // Size and arrow size is constant
+    $size="";
+    $arrowsize="";
+
+    // Since we have different scales we need the data points
+    // to be of the same magnitude to give it a distance
+    // interpretation.
+    $x *= 10; 
+
+    // Colors gets colder the further out we go from the center
+    $r = ($x-$polex*10)*($x-$polex*10)+($y-$poley)*($y-$poley);
+    $f = $r/$maxr;
+    if( $f > 1 ) $f=1;
+    $red = floor((1-$f)*255);
+    $blue = floor($f*255);
+    $color = array($red,0,$blue);
+    //echo "x=$x, y=$y, blue=$blue, red=$red<br>";
+    return array($color,$size,$arrowsize);
+}
+
+// Create data for a simulated pseudo-magnetic radient field
+$datax = array();
+$datay = array();
+$angle = array();
+for($x=1; $x < 10; ++$x ) {
+    for($y=10; $y<100; $y += 10) {
+	$a = -1;
+	if( $x==$polex && $y==$poley ) continue;
+	if( $x==$polex ) {
+	    if( $y > $poley ) $a=90;
+	    else $a = 270;
+	}
+	if( $y==$poley ) {
+	    if( $x  > $polex ) $a=0;
+	    else  $a=180;	    
+	}
+	if( $a == -1 ) {
+	    $d1 = $y-$poley;
+	    $d2 = ($polex-$x)*20;
+	    if( $y < $poley ) $d2 *= -1;
+	    $h = sqrt($d1*$d1+$d2*$d2);
+	    $t = -$d2/$h;
+	    $ac = acos($t);
+	    if( $y < $poley ) $ac += M_PI;
+	    $a = $ac * 180/M_PI;
+	}
+	$datax[] = $x;
+	$datay[] = $y;
+	$angle[] = $a;
+    }
+}
+
+// Setup the graph
+$graph = new Graph(300,200);
+$graph->SetScale("intlin",0,100,0,10);
+$graph->SetMarginColor('lightblue');
+
+
+// ..and titles
+$graph->title->Set("Field plot");
+
+// Setup the field plot
+$fp = new FieldPlot($datay,$datax,$angle);
+
+// Setup formatting callback
+$fp->SetCallback('FldCallback');
+
+// First size argument is length (in pixels of arrow) 
+// Second size argument is roughly size of arrow. Arrow size is specified as
+// an integer in the range [0,9]
+$fp->arrow->SetSize(20,2);
+$fp->arrow->SetColor('navy');
+
+$graph->Add($fp);
+
+// .. and output
+$graph->Stroke();
+
+?>
+
+