[dygraphs.git] / docs / index.html

<html>
  <head>
    <title>dygraphs JavaScript Library</title>
    <!--[if IE]>
    <script type="text/javascript" src="excanvas.js"></script>
    <![endif]-->
    <script type="text/javascript" src="dygraph-combined.js"></script>
    <style type="text/css">
      .thinborder {
        border-width: 1px;
        border-spacing: 0px;
        border-style: solid;
        border-color: black;
        border-collapse: collapse;
      }
      .thinborder td, .thinborder th {
        border-width: 1px;
        padding: 5px;
        border-style: solid;
        border-color: black;
      }
    </style>
  </head>
<body>
  <center>
    <p><span style="font-size:28pt;">dygraphs JavaScript Library</span><br/>
    <a href="http://code.google.com/p/dygraphs/">code.google.com/p/dygraphs</a></p>
  </center>

<p>The dygraphs JavaScript library produces produces interactive, zoomable charts of time series based on CSV files.</p>

<h3>Features</h3>
<ul>
  <li>Plots time series without using an external server or Flash</li>
  <li>Supports multiple data series</li>
  <li>Supports error bands around data series</li>
  <li>Displays values on mouseover</li>
  <li>Interactive zoom</li>
  <li>Adjustable averaging period</li>
  <li>Customizable click-through actions</li>
</ul>

<h3>Caveats</h3>
<ul>
  <li>Requires Firefox 1.5+ or Safari/WebKit 1.3+.</li>
  <li>Internet Explorer is poorly supported.</li>
</ul>

<h2>Demo</h2>
<font size=-1>(Mouse over to highlight individual values. Click and drag to zoom. Double-click to zoom out.)</font><br/>
<table><tr><td>
<div id="demodiv" style="width:480px; height:320px;"></div>
</td><td valign=top>
<div id="status" style="width:200px; font-size:0.8em; padding-top:5px;"></div>
</td>
</tr></table>
<script type="text/javascript">
  g = new DateGraph(
          document.getElementById("demodiv"),
          function() {
            var r = "date,parabola,line,another line,sine wave\n";
            for (var i=1; i<=31; i++) {
            r += "200610" + i;
            r += "," + 10*(i*(31-i));
            r += "," + 10*(8*i);
            r += "," + 10*(250 - 8*i);
            r += "," + 10*(125 + 125 * Math.sin(0.3*i));
            r += "\n";
            }
            return r;
          },
          null,
          {
            rollPeriod: 1,
            labelsDiv: document.getElementById('status'),
            labelsSeparateLines: true,
            labelsKMB: true,
            colors: ["hsl(180,60,50)",
                     "rgb(255,100,100)",
                     "#00DD55",
                     "rgba(50,50,200,0.4)"],
            padding: {left: 40, right: 30, top: 15, bottom: 15}
          }
      );
</script>

<h2>Usage</h2>

<p>The DateGraph library depends on two other JS libraries: <a href="http://www.mochikit.com/">MochiKit</a> and <a href="http://www.liquidx.net/plotkit/">PlotKit</a>. Rather than tracking down copies of these libraries, I recommend using a packed version of dygraphs that combines all three libraries into a single JS file. Either grab this file from dygraph project's <a href="http://code.google.com/p/dygraphs/downloads/list">downloads</a> page or create it yourself by <a href="http://code.google.com/p/dygraphs/source/checkout">checking out</a> a copy of the code and running:

<pre>./generate-combined.sh</pre>

<p>The combined JS file is now in <code>dygraph-combined.js</code>. Here's a basic example to get things started:</p>

<table>
  <tr><th>HTML</th>
      <td rowspan=2><img src=arrow.gif /></td>
      <th>Output</th></tr>
<tr>
<td valign=top><pre>
&lt;html&gt;
&lt;head&gt;
&lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;div id="graphdiv" style="width:400px; height:300px;"&gt;&lt;/div&gt;
&lt;script type="text/javascript"&gt;
  g = new DateGraph(
        document.getElementById("graphdiv"),  // containing div
        function() {                // function or path to CSV file.
          return "20080507,75\n" +
                 "20080508,70\n" +
                 "20080509,80\n";
        },
        [ "Temperature" ],          // names of data series
        {}                          // additional options (see below)
      );
&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
</pre>
</td><td valign=top>
  <div id="graphdiv" style="width:400px; height:300px;"></div>
  <script type="text/javascript">
    g = new DateGraph(
          document.getElementById("graphdiv"),
          function() {                          // function or path to CSV file.
            return "20080507,75\n" +
                   "20080508,70\n" +
                   "20080509,80\n";
          },
          [ "Temperature" ],                    // names of data series
          {}                                    // additional options
        );
  </script>
</td></tr></table>

<p>In order to keep this example self-contained, the second parameter is a function that returns CSV data. These lines <i>must</i> begin with a date in the form <i>YYYYMMDD</i>. In most applications, it makes more sense to include a CSV file instead. If the second parameter to the constructor is a string, it will be interpreted as the path to a CSV file. The DateGraph will perform an XMLHttpRequest to retrieve this file and display the data when it becomes available. Make sure your CSV file is readable and serving from a place that understands XMLHttpRequest's! In particular, you cannot specify a CSV file using <code>"file:///"</code>. Here's an example: (data from <a href="http://www.wunderground.com/history/airport/KNUQ/2007/1/1/CustomHistory.html?dayend=31&monthend=12&yearend=2007&req_city=NA&req_state=NA&req_statename=NA">Weather Underground</a>)</p>

<table>
  <tr><th>HTML</th>
      <td rowspan=2><img src=arrow.gif /></td>
      <th>Output</th></tr>
<tr>
<td valign=top><pre>
&lt;html&gt;
&lt;head&gt;
&lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;div id="graphdiv" style="width:600px; height:300px;"&gt;&lt;/div&gt;
&lt;script type="text/javascript"&gt;
  g = new DateGraph(
        document.getElementById("graphdiv"),
        "temperatures.csv",  // path to CSV file
        null,                // labels in top line of CSV file
        {}
      );
&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
</pre>
</td><td valign=top>
  <div id="graphdiv2" style="width:600px; height:300px;"></div>
  <script type="text/javascript">
    g2 = new DateGraph(
          document.getElementById("graphdiv2"),
          "temperatures.csv", null, {}
        );
  </script>
</td></tr></table>

<p>Click <a href="temperatures.csv">here</a> to view the <code>temperatures.csv</code> file. There are a few things to note here:</p>

<ul>
  <li>Because the third parameter to the DateGraph constructor was <code>null</code>, the labels were taken from the first line of the data instead. The first line of <code>temperatures.csv</code> is <code>Date,High,Low</code>.</li>
  <li>DateGraph automatically chose two different, easily-distinguishable colors for the two data series.</li>
  <li>The labels on the x-axis have switched from days to months. If you zoom in, they'll switch to weeks and then days.</li>
  <li>Some heuristics are used to determine a good vertical range for the data. The idea is to make all the data visible and have human-friendly values on the axis (i.e. 200 instead of 193.4). Generally this works well, but in this case the vertical range is way too large.</li>
  <li>The data is very spiky. A moving average would be easier to interpret.</li>
</ul>

<p>These last two problems can be fixed by specifying the appropriate options in the fourth parameter to the DateGraph constructor. To set the number of days for a moving average, use the <b>rollPeriod</b> option. To set the range of the y-axis, use the <b>valueRange</b> option. Here's how it's done:</p>

<table>
  <tr><th>HTML</th>
      <td rowspan=2><img src=arrow.gif /></td>
      <th>Output</th></tr>
<tr>
<td valign=top><pre>
&lt;html&gt;
&lt;head&gt;
&lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;div id="graphdiv" style="width:600px; height:300px;"&gt;&lt;/div&gt;
&lt;script type="text/javascript"&gt;
  g = new DateGraph(
        document.getElementById("graphdiv"),
        "temperatures.csv", null,
        { rollPeriod: 7,
          valueRange: [25, 100]
        }
      );
&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
</pre>
</td><td valign=top>
  <div id="graphdiv3" style="width:600px; height:300px;"></div>
  <script type="text/javascript">
    g3 = new DateGraph(
          document.getElementById("graphdiv3"),
          "temperatures.csv", null,
          { rollPeriod: 7,
            valueRange: [25, 100]
          }
        );
  </script>
</td></tr></table>

<p>A rolling average can always be set using the text box in the lower left-hand corner of the graph.</p>

<h2>Error Bars</h2>
<p>Another significant feature of the dygraphs library is the ability to display error bars around data series. One standard deviation must be specified for each data point. A +/-<i>n</i> sigma band will be drawn around the data series at that point. If a moving average is being displayed, DateGraph will compute the standard deviation of the average at each point. (i.e. <i>&sigma;</i> = sqrt((<i>&sigma;_1</i>^2 + <i>&sigma;_2</i>^2 + ... + <i>&sigma;_n</i>^2)/<i>n</i>))</p>

<p>Here's a demonstration. There are two data series. One is <code>N(100,10)</code> with a standard deviation of 10 specified at each point. The other is <code>N(80,20)</code> with a standard deviation of 20 specified at each point. The CSV file was generated using Octave and can be viewed <a href="twonormals.csv">here</a>.</p>

<table>
  <tr><th>HTML</th>
      <td rowspan=2><img src=arrow.gif /></td>
      <th>Output</th></tr>
<tr>
<td valign=top><pre>
&lt;html&gt;
&lt;head&gt;
&lt;script type="text/javascript"
  src="combined.js"&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;div id="graphdiv" 
 style="width:800px; height:400px;"
 &gt;&lt;/div&gt;
&lt;script type="text/javascript"&gt;
$ = document.getElementById;
g = new DateGraph(
  $("graphdiv"),
  "twonormals.csv",
  null,
  { rollPeriod: 7,
    errorBars: true,
    valueRange: [50,125]
  }
);
&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;
</pre>
</td><td valign=top>
  <div id="graphdiv4" style="width:800px; height:400px;"></div>
  <script type="text/javascript">
$ = document.getElementById;
new DateGraph(
  document.getElementById("graphdiv4"),
  "twonormals.csv",
  null,
  { rollPeriod: 14,
    errorBars: true,
    valueRange: [50, 125]
  }
);
  </script>
</td></tr></table>

<p>Things to note here:</p>
<ul>
  <li>The <b>errorBars</b> option affects both the interpretation of the CSV file and the display of the graph. When <b>errorBars</b> is set to true, each line is interpreted as <i>YYYYMMDD</i>,<i>A</i>,<i>sigma_A</i>,<i>B</i>,<i>sigma_B</i>,...</li>
  <li>The first line of the CSV file doesn't mention the error columns. In this case, it's just "Date,Series1,Series2".</li>
  <li>The averaging visibly affects the error bars. This is most clear if you crank up the rolling period to something like 100 days. For the earliest dates, there won't be 100 data points to average so the signal will be noisier. The error bars get smaller like sqrt(N) going forward in time until there's a full 100 points to average.</li>
  <li>The error bars are partially transparent. This can be seen when they overlap one another.</li>
</ul>

<h2>Other Options</h2>
<p>These are the options that can be passed in through the fourth parameter of the DateGraph constructor.</p>

<table class=thinborder width=1000>
  <tr><th>Name</th><th>Sample Value</th><th>Description</th></tr>
  <tr>
    <td><b>rollPeriod</b></td>
    <td><code>7</code></td>
    <td>Number of days over which to average data. Discussed extensively above.</td>
  </tr><tr>
    <td><b>colors</b></td>
    <td><code>['red',&nbsp;'#00FF00']</code></td>
    <td>List of colors for the data series. These can be of the form "#AABBCC"
      or "rgb(255,100,200)" or "yellow", etc. If not specified, equally-spaced
      points around a color wheel are used.</td>
  </tr><tr>
    <td><b>colorSaturation</b></td>
    <td><code>1.0</code></td>
    <td>If <b>colors</b> is not specified, saturation of the
      automatically-generated data series colors. (0.0-1.0, default:
      1.0)</td>
  </tr><tr>
    <td><b>colorValue</b></td>
    <td><code>0.5</code></td>
    <td>If colors is not specified, value of the data series colors, as in
      hue/saturation/value. (0.0-1.0, default 0.5)</td>
  </tr><tr>
    <td><b>clickCallback</b></td>
    <td><code>function(e,date){ alert(date); }</code></td>
    <td>A function to call when a data point is clicked. The function should take
      two arguments, the event object for the click and the date that was
      clicked. (default null)</td>
  </tr><tr>
    <td><b>errorBars</b></td>
    <td><code>false</code></td>
    <td>Does the data contain standard deviations? Setting this to true alters
      the input format (see above). (default false)</td>
  </tr><tr>
    <td><b>strokeWidth</b></td>
    <td><code>2.0</code></td>
    <td>Width of the data lines. This can be used to increase the contrast or
      some graphs. (default 1.0)</td>
  </tr><tr>
    <td><b>dateWindow</b></td>
    <td><code>[(new&nbsp;Date('2006-01-01')).valueOf(),<br/>
        (new&nbsp;Date()).valueOf()]</code></td>
    <td>Initially zoom in on a section of the graph. Is of the form [earliest,
      latest], where earliest/latest are millis since epoch.  By default, the
      full range of the input is shown.</td>
  </tr><tr>
    <td><b>valueRange</b></td>
    <td><code>[10, 110]</code></td>
    <td>Explicitly set the vertical range of the graph to [low, high]. By
      default, some clever heuristics are used (see above).</td>
  </tr><tr>
    <td><b>minTickSize</b></td>
    <td><code>1</code</td>
    <td>The difference between ticks on the y-axis can be greater than or equal
      to this, but no less. If you set it to 1, for instance, you'll never get
      nonintegral gaps between ticks.</td>
  </tr><tr>
    <td><b>labelsSeparateLines</b></td>
    <td><code>true</code></td>
    <td>Put &lt;br/&gt; between lines in the label string. Often used in
      conjunction with <b>labelsDiv</b>. (default false)</td>
  </tr><tr>
    <td><b>labelsDiv</b></td>
    <td><code>document.getElementById('foo')</code></td>
    <td>Show data labels in an external div, rather than on the graph. (default
      null)</td>
  </tr><tr>
    <td><b>labelsKMB</b></td>
    <td><code>true</code></td>
    <td>Show K/M/B for thousands/millions/billions on y-axis (default
      false).</td>
  </tr>
  <tr>
    <td><b>padding</b></td>
    <td><code>{left:&nbsp;40, right:&nbsp;30,<br/>top:&nbsp;5,
        bottom:&nbsp;15}</code></td>
    <td>Adds extra pixels of padding around the graph. Sometimes a dygraph
      gets clipped by surrounding text (see the Demo at the top of this page).
      Setting this property appropriately will fix this problem.</td>
  </tr>
</table>

<p>Any options you specify also get passed on to PlotKit's <a href="http://media.liquidx.net/js/plotkit-doc/PlotKit.Renderer.html">Renderer</a> class. DateGraph will override some of these (e.g. strokeColor), but others may be useful. The <code>padding</code> property is an example of this.</p>

<h2>Common Gotchas</h2>
<p>Here are a few problems that I've frequently run into while using the
dygraphs library.</p>

<ul>
  <li>Make sure your CSV files are readable! If your graph isn't showing up,
  the XMLHttpRequest for the CSV file may be failing. You can determine whether
  this is the case using tools like <a
    href="http://www.getfirebug.com/">Firebug</a>.</li>

  <li>Make sure your CSV files are in the correct format. They must be of the
  form <code>YYYYMMDD,series1,series2,...</code>. If you're specifying the
  names of each data series in the CSV file itself, make sure that you pass
  <code>null</code> as the third parameter to the DateGraph constructor to let
  the library know that. And if you set the <code>errorBars</code> property,
  make sure you alternate data series and standard deviations.</li>

  <li>dygraphs are not happy when placed inside a <code>&lt;center&gt;</code>
  tag. This applies to the CSS <code>text-align</code> property as well. If you
  want to center a DateGraph, put it inside a table with "align=center"
  set.</li>

  <li>If you specify the <code>colors</code> property or name the data series
  using the third parameter of the DateGraph constructor, make sure the number
  of data series agree in all places: <code>colors</code>, third parameter and
  in each line of the CSV file itself.</li>

  <li>Don't set the <code>dateWindow</code> property to a date. It expects
  milliseconds since epoch, which can be obtained from a JavaScript Date
  object's valueOf method.</li>
</ul>

<p><font size=-1>Created May 9, 2008 by <a href=mailto:danvdk@gmail.com>Dan Vanderkam</a></font></p>

</body>
</html>
Commit	Line	Data
078d1d29 DV	1	<html>
	2	<head>
	3	<title>dygraphs JavaScript Library</title>
	4	<!--[if IE]>
	5	<script type="text/javascript" src="excanvas.js"></script>
	6	<![endif]-->
9f006dbf	7	<script type="text/javascript" src="dygraph-combined.js"></script>
078d1d29 DV	8	<style type="text/css">
	9	.thinborder {
	10	border-width: 1px;
	11	border-spacing: 0px;
	12	border-style: solid;
	13	border-color: black;
	14	border-collapse: collapse;
	15	}
	16	.thinborder td, .thinborder th {
	17	border-width: 1px;
	18	padding: 5px;
	19	border-style: solid;
	20	border-color: black;
	21	}
	22	</style>
	23	</head>
	24	<body>
	25	<center>
52e5492a DV	26	<p><span style="font-size:28pt;">dygraphs JavaScript Library</span><br/>
52e5492a DV	27	<a href="http://code.google.com/p/dygraphs/">code.google.com/p/dygraphs</a></p>
078d1d29 DV	28	</center>
	29
	30	<p>The dygraphs JavaScript library produces produces interactive, zoomable charts of time series based on CSV files.</p>
	31
	32	<h3>Features</h3>
	33	<ul>
	34	<li>Plots time series without using an external server or Flash</li>
	35	<li>Supports multiple data series</li>
	36	<li>Supports error bands around data series</li>
	37	<li>Displays values on mouseover</li>
	38	<li>Interactive zoom</li>
	39	<li>Adjustable averaging period</li>
	40	<li>Customizable click-through actions</li>
	41	</ul>
	42
	43	<h3>Caveats</h3>
	44	<ul>
	45	<li>Requires Firefox 1.5+ or Safari/WebKit 1.3+.</li>
04aa50fd	46	<li>Internet Explorer is poorly supported.</li>
078d1d29 DV	47	</ul>
	48
	49	<h2>Demo</h2>
	50	<font size=-1>(Mouse over to highlight individual values. Click and drag to zoom. Double-click to zoom out.)</font><br/>
	51	<table><tr><td>
	52	<div id="demodiv" style="width:480px; height:320px;"></div>
	53	</td><td valign=top>
52e5492a	54	<div id="status" style="width:200px; font-size:0.8em; padding-top:5px;"></div>
078d1d29	55	</td>
6153f697	56	</tr></table>
078d1d29 DV	57	<script type="text/javascript">
	58	g = new DateGraph(
	59	document.getElementById("demodiv"),
	60	function() {
	61	var r = "date,parabola,line,another line,sine wave\n";
	62	for (var i=1; i<=31; i++) {
	63	r += "200610" + i;
	64	r += "," + 10(i(31-i));
	65	r += "," + 10(8i);
	66	r += "," + 10(250 - 8i);
	67	r += "," + 10(125 + 125 Math.sin(0.3*i));
	68	r += "\n";
	69	}
	70	return r;
	71	},
	72	null,
	73	{
	74	rollPeriod: 1,
	75	labelsDiv: document.getElementById('status'),
	76	labelsSeparateLines: true,
	77	labelsKMB: true,
	78	colors: ["hsl(180,60,50)",
	79	"rgb(255,100,100)",
	80	"#00DD55",
	81	"rgba(50,50,200,0.4)"],
52e5492a	82	padding: {left: 40, right: 30, top: 15, bottom: 15}
078d1d29 DV	83	}
	84	);
	85	</script>
	86
	87	<h2>Usage</h2>
	88
9f006dbf	89	<p>The DateGraph library depends on two other JS libraries: <a href="http://www.mochikit.com/">MochiKit</a> and <a href="http://www.liquidx.net/plotkit/">PlotKit</a>. Rather than tracking down copies of these libraries, I recommend using a packed version of dygraphs that combines all three libraries into a single JS file. Either grab this file from dygraph project's <a href="http://code.google.com/p/dygraphs/downloads/list">downloads</a> page or create it yourself by <a href="http://code.google.com/p/dygraphs/source/checkout">checking out</a> a copy of the code and running:
078d1d29	90
9f006dbf	91	<pre>./generate-combined.sh</pre>
078d1d29	92
9f006dbf	93	<p>The combined JS file is now in <code>dygraph-combined.js</code>. Here's a basic example to get things started:</p>
078d1d29 DV	94
	95	<table>
	96	<tr><th>HTML</th>
	97	<td rowspan=2><img src=arrow.gif /></td>
	98	<th>Output</th></tr>
	99	<tr>
	100	<td valign=top><pre>
	101	<html>
	102	<head>
	103	<script type="text/javascript" src="combined.js"></script>
	104	</head>
	105	<body>
	106	<div id="graphdiv" style="width:400px; height:300px;"></div>
	107	<script type="text/javascript">
	108	g = new DateGraph(
	109	document.getElementById("graphdiv"), // containing div
	110	function() { // function or path to CSV file.
	111	return "20080507,75\n" +
	112	"20080508,70\n" +
	113	"20080509,80\n";
	114	},
	115	[ "Temperature" ], // names of data series
	116	{} // additional options (see below)
	117	);
	118	</script>
	119	</body>
	120	</html>
	121	</pre>
	122	</td><td valign=top>
	123	<div id="graphdiv" style="width:400px; height:300px;"></div>
	124	<script type="text/javascript">
	125	g = new DateGraph(
	126	document.getElementById("graphdiv"),
	127	function() { // function or path to CSV file.
	128	return "20080507,75\n" +
	129	"20080508,70\n" +
	130	"20080509,80\n";
	131	},
	132	[ "Temperature" ], // names of data series
	133	{} // additional options
	134	);
	135	</script>
	136	</td></tr></table>
	137
	138	<p>In order to keep this example self-contained, the second parameter is a function that returns CSV data. These lines <i>must</i> begin with a date in the form <i>YYYYMMDD</i>. In most applications, it makes more sense to include a CSV file instead. If the second parameter to the constructor is a string, it will be interpreted as the path to a CSV file. The DateGraph will perform an XMLHttpRequest to retrieve this file and display the data when it becomes available. Make sure your CSV file is readable and serving from a place that understands XMLHttpRequest's! In particular, you cannot specify a CSV file using <code>"file:///"</code>. Here's an example: (data from <a href="http://www.wunderground.com/history/airport/KNUQ/2007/1/1/CustomHistory.html?dayend=31&monthend=12&yearend=2007&req_city=NA&req_state=NA&req_statename=NA">Weather Underground</a>)</p>
	139
	140	<table>
	141	<tr><th>HTML</th>
	142	<td rowspan=2><img src=arrow.gif /></td>
	143	<th>Output</th></tr>
	144	<tr>
	145	<td valign=top><pre>
	146	<html>
	147	<head>
	148	<script type="text/javascript" src="combined.js"></script>
	149	</head>
	150	<body>
	151	<div id="graphdiv" style="width:600px; height:300px;"></div>
	152	<script type="text/javascript">
	153	g = new DateGraph(
	154	document.getElementById("graphdiv"),
	155	"temperatures.csv", // path to CSV file
	156	null, // labels in top line of CSV file
	157	{}
158	);
159	</script>
160	</body>
161	</html>
162	</pre>
163	</td><td valign=top>
164	<div id="graphdiv2" style="width:600px; height:300px;"></div>
165	<script type="text/javascript">
166	g2 = new DateGraph(
167	document.getElementById("graphdiv2"),
168	"temperatures.csv", null, {}
169	);
170	</script>
171	</td></tr></table>
172
173	<p>Click <a href="temperatures.csv">here</a> to view the <code>temperatures.csv</code> file. There are a few things to note here:</p>
174
175	<ul>
176	<li>Because the third parameter to the DateGraph constructor was <code>null</code>, the labels were taken from the first line of the data instead. The first line of <code>temperatures.csv</code> is <code>Date,High,Low</code>.</li>
177	<li>DateGraph automatically chose two different, easily-distinguishable colors for the two data series.</li>
178	<li>The labels on the x-axis have switched from days to months. If you zoom in, they'll switch to weeks and then days.</li>
179	<li>Some heuristics are used to determine a good vertical range for the data. The idea is to make all the data visible and have human-friendly values on the axis (i.e. 200 instead of 193.4). Generally this works well, but in this case the vertical range is way too large.</li>
180	<li>The data is very spiky. A moving average would be easier to interpret.</li>
181	</ul>
182
183	<p>These last two problems can be fixed by specifying the appropriate options in the fourth parameter to the DateGraph constructor. To set the number of days for a moving average, use the <b>rollPeriod</b> option. To set the range of the y-axis, use the <b>valueRange</b> option. Here's how it's done:</p>
184
185	<table>
186	<tr><th>HTML</th>
187	<td rowspan=2><img src=arrow.gif /></td>
188	<th>Output</th></tr>
189	<tr>
190	<td valign=top><pre>
191	<html>
192	<head>
193	<script type="text/javascript" src="combined.js"></script>
194	</head>
195	<body>
196	<div id="graphdiv" style="width:600px; height:300px;"></div>
197	<script type="text/javascript">
198	g = new DateGraph(
199	document.getElementById("graphdiv"),
200	"temperatures.csv", null,
201	{ rollPeriod: 7,
202	valueRange: [25, 100]
203	}
204	);
205	</script>
206	</body>
207	</html>
208	</pre>
209	</td><td valign=top>
210	<div id="graphdiv3" style="width:600px; height:300px;"></div>
211	<script type="text/javascript">
212	g3 = new DateGraph(
213	document.getElementById("graphdiv3"),
214	"temperatures.csv", null,
215	{ rollPeriod: 7,
216	valueRange: [25, 100]
217	}
218	);
219	</script>
220	</td></tr></table>
221
222	<p>A rolling average can always be set using the text box in the lower left-hand corner of the graph.</p>
223
224	<h2>Error Bars</h2>
225	<p>Another significant feature of the dygraphs library is the ability to display error bars around data series. One standard deviation must be specified for each data point. A +/-<i>n</i> sigma band will be drawn around the data series at that point. If a moving average is being displayed, DateGraph will compute the standard deviation of the average at each point. (i.e. <i>σ</i> = sqrt((<i>σ_1</i>^2 + <i>σ_2</i>^2 + ... + <i>σ_n</i>^2)/<i>n</i>))</p>
226
227	<p>Here's a demonstration. There are two data series. One is <code>N(100,10)</code> with a standard deviation of 10 specified at each point. The other is <code>N(80,20)</code> with a standard deviation of 20 specified at each point. The CSV file was generated using Octave and can be viewed <a href="twonormals.csv">here</a>.</p>
228
229	<table>
230	<tr><th>HTML</th>
231	<td rowspan=2><img src=arrow.gif /></td>
232	<th>Output</th></tr>
233	<tr>
234	<td valign=top><pre>
235	<html>
236	<head>
237	<script type="text/javascript"
238	src="combined.js"></script>
239	</head>
240	<body>
241	<div id="graphdiv"
242	style="width:800px; height:400px;"
243	></div>
244	<script type="text/javascript">
245	$ = document.getElementById;
246	g = new DateGraph(
247	$("graphdiv"),
248	"twonormals.csv",
249	null,
250	{ rollPeriod: 7,
251	errorBars: true,
252	valueRange: [50,125]
253	}
254	);
255	</script>
256	</body>
257	</html>
258	</pre>
259	</td><td valign=top>
260	<div id="graphdiv4" style="width:800px; height:400px;"></div>
261	<script type="text/javascript">
262	$ = document.getElementById;
263	new DateGraph(
264	document.getElementById("graphdiv4"),
265	"twonormals.csv",
266	null,
267	{ rollPeriod: 14,
268	errorBars: true,
269	valueRange: [50, 125]
270	}
271	);
272	</script>
273	</td></tr></table>
274
275	<p>Things to note here:</p>
276	<ul>
277	<li>The <b>errorBars</b> option affects both the interpretation of the CSV file and the display of the graph. When <b>errorBars</b> is set to true, each line is interpreted as <i>YYYYMMDD</i>,<i>A</i>,<i>sigma_A</i>,<i>B</i>,<i>sigma_B</i>,...</li>
278	<li>The first line of the CSV file doesn't mention the error columns. In this case, it's just "Date,Series1,Series2".</li>
279	<li>The averaging visibly affects the error bars. This is most clear if you crank up the rolling period to something like 100 days. For the earliest dates, there won't be 100 data points to average so the signal will be noisier. The error bars get smaller like sqrt(N) going forward in time until there's a full 100 points to average.</li>
280	<li>The error bars are partially transparent. This can be seen when they overlap one another.</li>
281	</ul>
282
283	<h2>Other Options</h2>
284	<p>These are the options that can be passed in through the fourth parameter of the DateGraph constructor.</p>
285
286	<table class=thinborder width=1000>
287	<tr><th>Name</th><th>Sample Value</th><th>Description</th></tr>
288	<tr>
289	<td><b>rollPeriod</b></td>
290	<td><code>7</code></td>
291	<td>Number of days over which to average data. Discussed extensively above.</td>
292	</tr><tr>
293	<td><b>colors</b></td>
294	<td><code>['red', '#00FF00']</code></td>
295	<td>List of colors for the data series. These can be of the form "#AABBCC"
296	or "rgb(255,100,200)" or "yellow", etc. If not specified, equally-spaced
297	points around a color wheel are used.</td>
298	</tr><tr>
299	<td><b>colorSaturation</b></td>
300	<td><code>1.0</code></td>
301	<td>If <b>colors</b> is not specified, saturation of the
302	automatically-generated data series colors. (0.0-1.0, default:
303	1.0)</td>
304	</tr><tr>
305	<td><b>colorValue</b></td>
306	<td><code>0.5</code></td>
307	<td>If colors is not specified, value of the data series colors, as in
308	hue/saturation/value. (0.0-1.0, default 0.5)</td>
309	</tr><tr>
310	<td><b>clickCallback</b></td>
311	<td><code>function(e,date){ alert(date); }</code></td>
312	<td>A function to call when a data point is clicked. The function should take
313	two arguments, the event object for the click and the date that was
314	clicked. (default null)</td>
315	</tr><tr>
316	<td><b>errorBars</b></td>
317	<td><code>false</code></td>
318	<td>Does the data contain standard deviations? Setting this to true alters
319	the input format (see above). (default false)</td>
320	</tr><tr>
321	<td><b>strokeWidth</b></td>
322	<td><code>2.0</code></td>
323	<td>Width of the data lines. This can be used to increase the contrast or
324	some graphs. (default 1.0)</td>
325	</tr><tr>
326	<td><b>dateWindow</b></td>
327	<td><code>[(new Date('2006-01-01')).valueOf(),<br/>
328	(new Date()).valueOf()]</code></td>
329	<td>Initially zoom in on a section of the graph. Is of the form [earliest,
330	latest], where earliest/latest are millis since epoch. By default, the
331	full range of the input is shown.</td>
332	</tr><tr>
333	<td><b>valueRange</b></td>
334	<td><code>[10, 110]</code></td>
335	<td>Explicitly set the vertical range of the graph to [low, high]. By
336	default, some clever heuristics are used (see above).</td>
337	</tr><tr>
338	<td><b>minTickSize</b></td>
339	<td><code>1</code</td>
340	<td>The difference between ticks on the y-axis can be greater than or equal
341	to this, but no less. If you set it to 1, for instance, you'll never get
342	nonintegral gaps between ticks.</td>
343	</tr><tr>
344	<td><b>labelsSeparateLines</b></td>
345	<td><code>true</code></td>
346	<td>Put <br/> between lines in the label string. Often used in
347	conjunction with <b>labelsDiv</b>. (default false)</td>
348	</tr><tr>
349	<td><b>labelsDiv</b></td>
350	<td><code>document.getElementById('foo')</code></td>
351	<td>Show data labels in an external div, rather than on the graph. (default
352	null)</td>
353	</tr><tr>
354	<td><b>labelsKMB</b></td>
355	<td><code>true</code></td>
356	<td>Show K/M/B for thousands/millions/billions on y-axis (default
357	false).</td>
358	</tr>
359	<tr>
360	<td><b>padding</b></td>
361	<td><code>{left: 40, right: 30,<br/>top: 5,
362	bottom: 15}</code></td>
363	<td>Adds extra pixels of padding around the graph. Sometimes a dygraph
364	gets clipped by surrounding text (see the Demo at the top of this page).
365	Setting this property appropriately will fix this problem.</td>
366	</tr>
367	</table>
368
369	<p>Any options you specify also get passed on to PlotKit's <a href="http://media.liquidx.net/js/plotkit-doc/PlotKit.Renderer.html">Renderer</a> class. DateGraph will override some of these (e.g. strokeColor), but others may be useful. The <code>padding</code> property is an example of this.</p>
370
371	<h2>Common Gotchas</h2>
372	<p>Here are a few problems that I've frequently run into while using the
373	dygraphs library.</p>
374
375	<ul>
376	<li>Make sure your CSV files are readable! If your graph isn't showing up,
377	the XMLHttpRequest for the CSV file may be failing. You can determine whether
378	this is the case using tools like <a
379	href="http://www.getfirebug.com/">Firebug</a>.</li>
380
381	<li>Make sure your CSV files are in the correct format. They must be of the
382	form <code>YYYYMMDD,series1,series2,...</code>. If you're specifying the
383	names of each data series in the CSV file itself, make sure that you pass
384	<code>null</code> as the third parameter to the DateGraph constructor to let
385	the library know that. And if you set the <code>errorBars</code> property,
386	make sure you alternate data series and standard deviations.</li>
387
388	<li>dygraphs are not happy when placed inside a <code><center></code>
389	tag. This applies to the CSS <code>text-align</code> property as well. If you
390	want to center a DateGraph, put it inside a table with "align=center"
391	set.</li>
392
393	<li>If you specify the <code>colors</code> property or name the data series
394	using the third parameter of the DateGraph constructor, make sure the number
395	of data series agree in all places: <code>colors</code>, third parameter and
396	in each line of the CSV file itself.</li>
397
398	<li>Don't set the <code>dateWindow</code> property to a date. It expects
399	milliseconds since epoch, which can be obtained from a JavaScript Date
400	object's valueOf method.</li>
401	</ul>
402
403	<p><font size=-1>Created May 9, 2008 by <a href=mailto:danvdk@gmail.com>Dan Vanderkam</a></font></p>
404
405	</body>
406	</html>