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   3     <title>dygraphs JavaScript Library</title>
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  25   <center>
  26     <p><span style="font-size:28pt;">dygraphs JavaScript Library</span><br/>
  27     <a href="http://code.google.com/p/dygraphs/">code.google.com/p/dygraphs</a></p>
  28   </center>
  29
  30 <p>The dygraphs JavaScript library produces produces interactive, zoomable charts of time series.</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   <li>Compatible with the Google Visualization API</li>
  42 </ul>
  43
  44 <h3>Caveats</h3>
  45 <ul>
  46   <li>Requires Firefox 1.5+ or Safari/WebKit 1.3+.</li>
  47   <li>Internet Explorer is poorly supported.</li>
  48 </ul>
  49
  50 <h2>Demo</h2>
  51 <font size=-1>(Mouse over to highlight individual values. Click and drag to zoom. Double-click to zoom out.)</font><br/>
  52 <table><tr><td>
  53 <div id="demodiv" style="width:480px; height:320px;"></div>
  54 </td><td valign=top>
  55 <div id="status" style="width:200px; font-size:0.8em; padding-top:5px;"></div>
  56 </td>
  57 </tr></table>
  58 <script type="text/javascript">
  59   g = new DateGraph(
  60           document.getElementById("demodiv"),
  61           function() {
  62             var zp = function(x) { if (x < 10) return "0"+x; else return x; };
  63             var r = "date,parabola,line,another line,sine wave\n";
  64             for (var i=1; i<=31; i++) {
  65             r += "200610" + zp(i);
  66             r += "," + 10*(i*(31-i));
  67             r += "," + 10*(8*i);
  68             r += "," + 10*(250 - 8*i);
  69             r += "," + 10*(125 + 125 * Math.sin(0.3*i));
  70             r += "\n";
  71             }
  72             return r;
  73           },
  74           null,
  75           {
  76             rollPeriod: 1,
  77             labelsDiv: document.getElementById('status'),
  78             labelsSeparateLines: true,
  79             labelsKMB: true,
  80             colors: ["hsl(180,60,50)",
  81                      "rgb(255,100,100)",
  82                      "#00DD55",
  83                      "rgba(50,50,200,0.4)"],
  84             padding: {left: 40, right: 30, top: 15, bottom: 15}
  85           }
  86       );
  87 </script>
  88
  89 <h2>Usage</h2>
  90
  91 <p>The dygraphs 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:
  92
  93 <pre>./generate-combined.sh</pre>
  94
  95 <p>The combined JS file is now in <code>dygraph-combined.js</code>. Here's a basic example to get things started:</p>
  96
  97 <table>
  98   <tr><th>HTML</th>
  99       <td rowspan=2><img src=arrow.gif /></td>
 100       <th>Output</th></tr>
 101 <tr>
 102 <td valign=top><pre>
 103 &lt;html&gt;
 104 &lt;head&gt;
 105 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 106 &lt;/head&gt;
 107 &lt;body&gt;
 108 &lt;div id="graphdiv"&gt;&lt;/div&gt;
 109 &lt;script type="text/javascript"&gt;
 110   g = new Dygraph(
 111         document.getElementById("graphdiv"),  // containing div
 112         "Date,Temperature\n" +                // CSV or path to a CSV file.
 113         "20080507,75\n" +
 114         "20080508,70\n" +
 115         "20080509,80\n",
 116       );
 117 &lt;/script&gt;
 118 &lt;/body&gt;
 119 &lt;/html&gt;
 120 </pre>
 121 </td><td valign=top>
 122   <div id="graphdiv"></div>
 123   <script type="text/javascript">
 124     g = new Dygraph(
 125         document.getElementById("graphdiv"),  // containing div
 126         "Date,Temperature\n" +                // CSV or path to a CSV file.
 127         "20080507,75\n" +
 128         "20080508,70\n" +
 129         "20080509,80\n"
 130       );
 131   </script>
 132 </td></tr></table>
 133
 134 <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 Dygraph 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>
 135
 136 <table>
 137   <tr><th>HTML</th>
 138       <td rowspan=2><img src=arrow.gif /></td>
 139       <th>Output</th></tr>
 140 <tr>
 141 <td valign=top><pre>
 142 &lt;html&gt;
 143 &lt;head&gt;
 144 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 145 &lt;/head&gt;
 146 &lt;body&gt;
 147 &lt;div id="graphdiv" style="width:600px; height:300px;"&gt;&lt;/div&gt;
 148 &lt;script type="text/javascript"&gt;
 149   g = new Dygraph(
 150         document.getElementById("graphdiv"),
 151         "temperatures.csv",  // path to CSV file
 152         {}                   // additional options
 153       );
 154 &lt;/script&gt;
 155 &lt;/body&gt;
 156 &lt;/html&gt;
 157 </pre>
 158 </td><td valign=top>
 159   <div id="graphdiv2" style="width:600px; height:300px;"></div>
 160   <script type="text/javascript">
 161     g2 = new Dygraph(
 162           document.getElementById("graphdiv2"),
 163           "temperatures.csv", {}
 164         );
 165   </script>
 166 </td></tr></table>
 167
 168 <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>
 169
 170 <ul>
 171   <li>The Dygraph sent off an XHR to get the temperatures.csv file.</li>
 172   <li>The labels were taken from the first line of <code>temperatures.csv</code>, which is <code>Date,High,Low</code>.</li>
 173   <li>The Dygraph automatically chose two different, easily-distinguishable colors for the two data series.</li>
 174   <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>
 175   <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.</li>
 176   <li>The data is very spiky. A moving average would be easier to interpret.</li>
 177 </ul>
 178
 179 <p>This problem can be fixed by specifying the appropriate options in the "additional options" parameter to the Dygraph constructor. To set the number of days for a moving average, use the <b>rollPeriod</b> option. Here's how it's done:</p>
 180
 181 <table>
 182   <tr><th>HTML</th>
 183       <td rowspan=2><img src=arrow.gif /></td>
 184       <th>Output</th></tr>
 185 <tr>
 186 <td valign=top><pre>
 187 &lt;html&gt;
 188 &lt;head&gt;
 189 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 190 &lt;/head&gt;
 191 &lt;body&gt;
 192 &lt;div id="graphdiv" style="width:600px; height:300px;"&gt;&lt;/div&gt;
 193 &lt;script type="text/javascript"&gt;
 194   g = new Dygraph(
 195         document.getElementById("graphdiv"),
 196         "temperatures.csv",
 197         { rollPeriod: 7,
 198           showRoller: true,
 199         }
 200       );
 201 &lt;/script&gt;
 202 &lt;/body&gt;
 203 &lt;/html&gt;
 204 </pre>
 205 </td><td valign=top>
 206   <div id="graphdiv3" style="width:600px; height:300px;"></div>
 207   <script type="text/javascript">
 208     g3 = new Dygraph(
 209           document.getElementById("graphdiv3"),
 210           "temperatures.csv",
 211           { rollPeriod: 7,
 212             showRoller: true,
 213           }
 214         );
 215   </script>
 216 </td></tr></table>
 217
 218 <p>A rolling average can be set using the text box in the lower left-hand corner of the graph (the showRoller attribute is what makes this appear).</p>
 219
 220 <h2>Error Bars</h2>
 221 <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, dygraphs 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>
 222
 223 <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>
 224
 225 <table>
 226   <tr><th>HTML</th>
 227       <td rowspan=2><img src=arrow.gif /></td>
 228       <th>Output</th></tr>
 229 <tr>
 230 <td valign=top><pre>
 231 &lt;html&gt;
 232 &lt;head&gt;
 233 &lt;script type="text/javascript"
 234   src="combined.js"&gt;&lt;/script&gt;
 235 &lt;/head&gt;
 236 &lt;body&gt;
 237 &lt;div id="graphdiv"
 238  style="width:800px; height:400px;"
 239  &gt;&lt;/div&gt;
 240 &lt;script type="text/javascript"&gt;
 241 $ = document.getElementById;
 242 g = new Dygraph(
 243   $("graphdiv"),
 244   "twonormals.csv",
 245   { rollPeriod: 7,
 246     showRoller: true,
 247     errorBars: true,
 248     valueRange: [50,125]
 249   }
 250 );
 251 &lt;/script&gt;
 252 &lt;/body&gt;
 253 &lt;/html&gt;
 254 </pre>
 255 </td><td valign=top>
 256   <div id="graphdiv4" style="width:800px; height:400px;"></div>
 257   <script type="text/javascript">
 258 $ = document.getElementById;
 259 new Dygraph(
 260   document.getElementById("graphdiv4"),
 261   "twonormals.csv",
 262   { rollPeriod: 14,
 263     showRoller: true,
 264     errorBars: true,
 265     valueRange: [50, 125]
 266   }
 267 );
 268   </script>
 269 </td></tr></table>
 270
 271 <p>Things to note here:</p>
 272 <ul>
 273   <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>
 274   <li>The first line of the CSV file doesn't mention the error columns. In this case, it's just "Date,Series1,Series2".</li>
 275   <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>
 276   <li>The error bars are partially transparent. This can be seen when they overlap one another.</li>
 277 </ul>
 278
 279 <h2>One last demo</h2>
 280
 281 <p>This chart shows monthly closes of the Dow Jones Industrial Average, both in nominal and real (i.e. adjusted for inflation) dollars. The shaded areas show its monthly high and low. CPI values with a base from 1982-84 are used to adjust for inflation.</p>
 282
 283 <div id=dow_chart style="width:1000px; height:400px;"></div>
 284 <script type="text/javascript">
 285   // From http://www.econstats.com/eqty/eq_d_mi_3.csv
 286   dow = new Dygraph(
 287     document.getElementById('dow_chart'),
 288     "dow.txt",
 289     {
 290       showRoller: true,
 291       customBars: true,
 292       labelsKMB: true,
 293       padding: {left:30, right:30, top:5, bottom:5}
 294     });
 295 </script>
 296
 297
 298 <h2>Other Options</h2>
 299 <p>These are the options that can be passed in through the optional third parameter of the Dygraph constructor.</p>
 300
 301 <table class=thinborder width=1000>
 302   <tr><th>Name</th><th>Sample Value</th><th>Description</th></tr>
 303   <tr>
 304     <td><b>rollPeriod</b></td>
 305     <td><code>7</code></td>
 306     <td>Number of days over which to average data. Discussed extensively above.</td>
 307   </tr><tr>
 308     <td><b>showRoller</b></td>
 309     <td><code>true</code></td>
 310     <td>Should the rolling average period text box be shown? Default is false.</td>
 311   </tr><tr>
 312     <td><b>colors</b></td>
 313     <td><code>['red',&nbsp;'#00FF00']</code></td>
 314     <td>List of colors for the data series. These can be of the form "#AABBCC"
 315       or "rgb(255,100,200)" or "yellow", etc. If not specified, equally-spaced
 316       points around a color wheel are used.</td>
 317   </tr><tr>
 318     <td><b>colorSaturation</b></td>
 319     <td><code>1.0</code></td>
 320     <td>If <b>colors</b> is not specified, saturation of the
 321       automatically-generated data series colors. (0.0-1.0, default:
 322       1.0)</td>
 323   </tr><tr>
 324     <td><b>colorValue</b></td>
 325     <td><code>0.5</code></td>
 326     <td>If colors is not specified, value of the data series colors, as in
 327       hue/saturation/value. (0.0-1.0, default 0.5)</td>
 328   </tr><tr>
 329     <td><b>clickCallback</b></td>
 330     <td><code>function(e,date){ alert(date); }</code></td>
 331     <td>A function to call when a data point is clicked. The function should take
 332       two arguments, the event object for the click and the date that was
 333       clicked. (default null)</td>
 334   </tr><tr>
 335     <td><b>errorBars</b></td>
 336     <td><code>false</code></td>
 337     <td>Does the data contain standard deviations? Setting this to true alters
 338       the input format (see above). (default false)</td>
 339   </tr><tr>
 340     <td><b>strokeWidth</b></td>
 341     <td><code>2.0</code></td>
 342     <td>Width of the data lines. This can be used to increase the contrast or
 343       some graphs. (default 1.0)</td>
 344   </tr><tr>
 345     <td><b>dateWindow</b></td>
 346     <td><code>[(new&nbsp;Date('2006-01-01')).valueOf(),<br/>
 347         (new&nbsp;Date()).valueOf()]</code></td>
 348     <td>Initially zoom in on a section of the graph. Is of the form [earliest,
 349       latest], where earliest/latest are millis since epoch.  By default, the
 350       full range of the input is shown.</td>
 351   </tr><tr>
 352     <td><b>valueRange</b></td>
 353     <td><code>[10, 110]</code></td>
 354     <td>Explicitly set the vertical range of the graph to [low, high]. By
 355       default, some clever heuristics are used (see above).</td>
 356   </tr><tr>
 357     <td><b>minTickSize</b></td>
 358     <td><code>1</code</td>
 359     <td>The difference between ticks on the y-axis can be greater than or equal
 360       to this, but no less. If you set it to 1, for instance, you'll never get
 361       nonintegral gaps between ticks.</td>
 362   </tr><tr>
 363     <td><b>labelsSeparateLines</b></td>
 364     <td><code>true</code></td>
 365     <td>Put &lt;br/&gt; between lines in the label string. Often used in
 366       conjunction with <b>labelsDiv</b>. (default false)</td>
 367   </tr><tr>
 368     <td><b>labelsDiv</b></td>
 369     <td><code>document.getElementById('foo')</code></td>
 370     <td>Show data labels in an external div, rather than on the graph. (default
 371       null)</td>
 372   </tr><tr>
 373     <td><b>labelsKMB</b></td>
 374     <td><code>true</code></td>
 375     <td>Show K/M/B for thousands/millions/billions on y-axis (default
 376       false).</td>
 377   </tr>
 378   <tr>
 379     <td><b>padding</b></td>
 380     <td><code>{left:&nbsp;40, right:&nbsp;30,<br/>top:&nbsp;5,
 381         bottom:&nbsp;15}</code></td>
 382     <td>Adds extra pixels of padding around the graph. Sometimes a dygraph
 383       gets clipped by surrounding text (see the Demo at the top of this page).
 384       Setting this property appropriately will fix this problem.</td>
 385   </tr>
 386 </table>
 387
 388 <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. dygraphs will override some of these (e.g. strokeColor), but others may be useful. The <code>padding</code> property is an example of this.</p>
 389
 390 <h2>Common Gotchas</h2>
 391 <p>Here are a few problems that I've frequently run into while using the
 392 dygraphs library.</p>
 393
 394 <ul>
 395   <li>Make sure your CSV files are readable! If your graph isn't showing up,
 396   the XMLHttpRequest for the CSV file may be failing. You can determine whether
 397   this is the case using tools like <a
 398     href="http://www.getfirebug.com/">Firebug</a>.</li>
 399
 400   <li>Make sure your CSV files are in the correct format. They must be of the
 401   form <code>YYYYMMDD,series1,series2,...</code>. And if you set the
 402   <code>errorBars</code> property, make sure you alternate data series and
 403   standard deviations.</li>
 404
 405   <li>dygraphs are not happy when placed inside a <code>&lt;center&gt;</code>
 406   tag. This applies to the CSS <code>text-align</code> property as well. If you
 407   want to center a Dygraph, put it inside a table with "align=center"
 408   set.</li>
 409
 410   <li>Don't set the <code>dateWindow</code> property to a date. It expects
 411   milliseconds since epoch, which can be obtained from a JavaScript Date
 412   object's valueOf method.</li>
 413 </ul>
 414
 415 <p><font size=-1>Created May 9, 2008 by <a href=mailto:danvdk@gmail.com>Dan Vanderkam</a></font></p>
 416
 417 </body>
 418 </html>