gallery/plotter.js

   1 // Use this as a template for new Gallery entries.
   2 Gallery.register(
   3   'plotter',
   4   {
   5     name: 'Function Plotter',
   6     title: 'Define your data with functions',
   7     setup: function(parent) {
   8       parent.innerHTML = [
   9         "<p><b>Equation: </b><br/>",
  10         "<textarea cols='80' rows='10' id='eq'>function(x) {",
  11         "  return [0.1 * x, 0.1 * x + Math.sin(x), 0.1*x + Math.cos(x)];",
  12         "}</textarea><br/>",
  13         "<b>Preset functions:</b> <select id='presets'>",
  14         "<option id='custom'>(custom)</option>",
  15         "<option id='id'>Identity</option>",
  16         "<option id='sine'>Sine Wave</option>",
  17         "<option id='taylor'>Taylor series</option>",
  18         "<option selected id='sawtooth'>Sawtooth</option>",
  19         "</select>",
  20         "</p>",
  21         "",
  22         "<p><b>x range: </b> <input type='text' width='5' id='x1' value='-10' />",
  23         "to <input type='text' width='5' id='x2' value='10' /></p>",
  24         "<p><button id='plot'>Plot</button></p>",
  25         "",
  26         "<div id='graph_div' style='width:600px; height:300px;'></div>"].join("\n");
  27
  28     },
  29     run: function() {
  30       var select = document.getElementById("presets");
  31       select.onchange = function() {
  32         var sel = select.selectedIndex;
  33         var id = select.options[sel].id;
  34         var presets = {
  35           'id': [ -10, 10, 'function(x) {\n  return x;\n}' ],
  36           'sine': [ -10, 10, 'function(x) {\n  return Math.sin(x);\n}' ],
  37           'taylor': [ -3, 3, 'function(x) {\n  return [Math.cos(x), 1 - x*x/2 + x*x*x*x/24];\n}' ],
  38           'sawtooth': [-10, 10, 'function(x) {\n  var y = 0;\n  for (var i = 1; i < 20; i+=2) {\n    y += Math.sin(i * x)/i;\n  }\n  var final = 1 - 2*(Math.abs(Math.floor(x / Math.PI)) % 2);\n  return [4/Math.PI * y, final];\n}' ]
  39         };
  40
  41         if (id == "custom") { return; }
  42         document.getElementById("x1").value = presets[id][0];
  43         document.getElementById("x2").value = presets[id][1];
  44         document.getElementById("eq").value = presets[id][2];
  45         plot();
  46       }
  47
  48       var plotButton = document.getElementById("plot");
  49       var plot = function() {
  50         var eq = document.getElementById("eq").value;
  51         eval("fn = " + eq);
  52
  53         var graph = document.getElementById("graph_div");
  54         var width = parseInt(graph.style.width);
  55         var x1 = parseFloat(document.getElementById("x1").value);
  56         var x2 = parseFloat(document.getElementById("x2").value);
  57         var xs = 1.0 * (x2 - x1) / width;
  58
  59         var data = [];
  60         for (var i = 0; i < width; i++) {
  61           var x = x1 + i * xs;
  62           var y = fn(x);
  63           var row = [x];
  64           if (y.length > 0) {
  65             for (var j = 0; j < y.length; j++) {
  66               row.push(y[j]);
  67             }
  68           } else {
  69             row.push(y);
  70           }
  71           data.push(row);
  72         }
  73
  74         g = new Dygraph(graph, data);
  75       }
  76       plot.onclick = plot;
  77       plot();
  78     }
  79   });