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  30       <h2>Documentation</h2>
  31       <ul>
  32         <li><a href="#demo">Demo</a></li>
  33         <li><a href="#usage">Usage</a></li>
  34         <li><a href="#ie">IE Compatibility</a></li>
  35         <li><a href="#gviz">GViz Data</a></li>
  36         <li><a href="#baseball">Baseball chart</a></li>
  37         <li><a href="#stock">Stock chart</a></li>
  38         <li><a href="#gwt">GWT Compatibility</a></li>
  39         <li><a href="#policy">Data Policy</a></li>
  40         <li><a href="options.html">Options Reference</a></li>
  41         <li><a href="jsdoc/symbols/Dygraph.html">JSDoc Reference</a></li>
  42         <li><a href="data.html">Data Formats</a></li>
  43         <li><a href="annotations.html">Annotations</a></li>
  44       </ul>
  45
  46       <h2>Project</h2>
  47       <ul>
  48         <li><a href="http://blog.dygraphs.com/">Blog</a></li>
  49         <li><a href="http://github.com/danvk/dygraphs">Source</a></li>
  50         <li><a href="http://code.google.com/p/dygraphs/issues/">Issues</a></li>
  51         <li><a href="http://code.google.com/p/dygraphs/issues/entry">Report Bug</a></li>
  52         <li><a href="changes.html">Contribute a change</a></li>
  53         <li><a href="mailto:dygraphs-users [at] googlegroups.com">Contact</a></li>
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  55
  56       <h2>Demos/Usage</h2>
  57       <ul>
  58         <li><a href="#users">Known Users</a></li>
  59         <hr/>
  60         <li><span style="color: red;">New!</span> <a href="gallery/">(browse gallery)</a></li>
  61         <li><a href="tests/">(browse demos)</a></li>
  62         <li><a href="tests/demo.html">Basic Demo</a></li>
  63         <li><a href="tests/gviz.html">GViz Demo</a></li>
  64         <li><a href="tests/plotter.html">Equation Plotter</a></li>
  65         <li><a href="tests/perf.html">Performance Test</a></li>
  66         <li><a href="tests/annotation.html">Annotations</a></li>
  67         <li><a href="tests/annotation-gviz.html">Annotations (GViz)</a></li>
  68         <li><a href="tests/fillGraph.html">Filled Chart</a></li>
  69         <li><a href="tests/perf.html">Fractions</a></li>
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  71         <li><a href="tests/label-div.html">Labels in a DIV</a></li>
  72         <li><a href="tests/numeric-axis.html">Numeric Axis</a></li>
  73         <li><a href="tests/draw-points.html">Dotted Points</a></li>
  74         <li><a href="tests/native-format.html">Native Format</a></li>
  75         <li><a href="tests/grid_dot.html">Crazy Styles</a></li>
  76         <li><a href="tests/spacing.html">Tick spacing</a></li>
  77         <li><a href="tests/callback.html">Callbacks</a></li>
  78         <li><a href="tests/hourly.html">Hourly/Minutely data</a></li>
  79         <li><a href="tests/isolated-points.html">Isolated Points</a></li>
  80         <li><a href="tests/missing-data.html">Missing Data</a></li>
  81         <li><a href="tests/border.html">Bordered chart</a></li>
  82         <li><a href="tests/custom-bars.html">Custom Bars</a></li>
  83         <li><a href="tests/customLabel.html">Custom Label Styles</a></li>
  84         <li><a href="tests/dygraph.html">Minimal Example</a></li>
  85         <li><a href="tests/negative.html">Negative Numbers</a></li>
  86         <li><a href="tests/highlighted-region.html">Custom Underlay / background</a></li>
  87         <li><a href="tests/zoom.html">Tests for zoom operations</a></li>
  88         <li><a href="tests/logscale.html">Log scale tests</a></li>
  89       </ul>
  90     </div>
  91
  92     <div id="content">
  93       <h1>dygraphs JavaScript Visualization Library</h1>
  94
  95       <p><a href="http://github.com/danvk/dygraphs">http://github.com/danvk/dygraphs</a></p>
  96       <p>See <a href="http://blog.dygraphs.com/">blog</a>, <a href="http://groups.google.com/group/dygraphs-users">mailing list</a>, <a href="http://github.com/danvk/dygraphs/downloads/">downloads</a>, <a href="tests/">demos</a> and <a href="http://code.google.com/p/dygraphs/issues/">open issues</a></p>
  97
  98       <p>dygraphs is an open source JavaScript library that produces produces interactive, zoomable charts of time series. It is designed to display dense data sets and enable users to explore and interpret them.</p>
  99
 100       <h3 id="demo">A demo is worth a thousand words:</h3>
 101
 102       <p style="font-size:0.8em">(Mouse over to highlight individual values. Click and drag to zoom. Double-click to zoom back out. Change the number and hit enter to adjust the averaging period.)</p>
 103
 104       <div id="demodiv" style="width:800px; height:320px;"></div>
 105       <script type="text/javascript">
 106         g = new Dygraph(
 107           document.getElementById("demodiv"),
 108           "ny-vs-sf.txt",
 109           {
 110             rollPeriod: 14,
 111             showRoller: true,
 112             customBars: true,
 113             title: 'Daily Temperatures in New York vs. San Francisco',
 114             ylabel: 'Temperature (F)',
 115             legend: 'always',
 116             labelsDivStyles: { 'textAlign': 'right' }
 117           }
 118         );
 119       </script>
 120
 121       <h4>Some things to notice:</h4>
 122       <ul>
 123         <li>There's less seasonal temperature variation in SF than in NY.</li>
 124         <li>The difference is about 15&deg; F for SF vs. 50&deg; F for NY.</li>
 125         <li>The daily data (set rolling period to 1) is quite noisy and hides this conclusion.</li>
 126         <li>Using a 14-day moving average makes it clearer. A 100-day rolling period averages out nearly all the specifics from the data.</li>
 127         <li>There's a gap in the data for SF, when the weather station was down (zoom into October 2007 to see it).</li>
 128         <li>The bands around each point indicate average highs and lows.</li>
 129         <li>There is a <em>lot</em> of data in this chart: low, average and high for each city on each day of a three year period &asymp; 6000 data points in all.</li>
 130       </ul>
 131
 132       <p>dygraphs allows the user to explore the data and discover these facts.</p>
 133
 134       <p>For more demos, browse the dygraph <a href="tests/">tests</a>
 135       directory. To see other people who are using dygraphs, check out the <a
 136       href="#users">known users</a>.</p>
 137
 138       <h3>Features</h3>
 139       <p>Some of the features of dygraphs:</p>
 140       <ul>
 141         <li>Plots time series without using an external server or Flash</li>
 142         <li>Works in Internet Explorer (using excanvas)</li>
 143         <li>Lightweight (69kb) and responsive</li>
 144         <li>Displays values on mouseover, making interaction easily discoverable</li>
 145         <li>Supports error bands around data series</li>
 146         <li>Interactive zoom</li>
 147         <li>Displays Annotations on the chart</li>
 148         <li>Adjustable averaging period</li>
 149         <li>Can intelligently chart fractions</li>
 150         <li>Customizable click-through actions</li>
 151         <li>Compatible with the Google Visualization API</li>
 152         <li>Intelligent defaults make it easy to use</li>
 153       </ul>
 154
 155       <h2 id="usage">Usage</h2>
 156
 157       <p>To use dygraphs, include the <code><a href="http://github.com/danvk/dygraphs/downloads/">dygraph-combined.js</a></code> JavaScript file and instantiate a <code>Dygraph</code> object.</p>
 158
 159       <p>Here's a basic example to get things started:</p>
 160
 161       <div class="example" style="clear:both;">
 162         <div class="codeblock" style="float:left;width:400px;">
 163           <h3 style="text-align:center">HTML</h3>
 164           <code>
 165   <pre>
 166 &lt;html&gt;
 167 &lt;head&gt;
 168 &lt;script type=&quot;text/javascript&quot;
 169   src=&quot;dygraph-combined.js&quot;&gt;&lt;/script&gt;
 170 &lt;/head&gt;
 171 &lt;body&gt;
 172 &lt;div id=&quot;graphdiv&quot;&gt;&lt;/div&gt;
 173 &lt;script type=&quot;text/javascript&quot;&gt;
 174   g = new Dygraph(
 175
 176     // containing div
 177     document.getElementById(&quot;graphdiv&quot;),
 178
 179     // CSV or path to a CSV file.
 180     &quot;Date,Temperature\n&quot; +
 181     &quot;2008-05-07,75\n&quot; +
 182     &quot;2008-05-08,70\n&quot; +
 183     &quot;2008-05-09,80\n&quot;
 184
 185   );
 186 &lt;/script&gt;
 187 &lt;/body&gt;
 188 &lt;/html&gt;
 189 </pre>
 190           </code>
 191         </div>
 192         <div class="codeoutput" style="float:left;">
 193           <h3 style="text-align:center">OUTPUT</h3>
 194           <div id="graphdiv"></div>
 195           <script type="text/javascript">
 196             g = new Dygraph(
 197
 198               // containing div
 199               document.getElementById("graphdiv"),
 200
 201               // CSV or path to a CSV file.
 202               "Date,Temperature\n" +
 203               "2008-05-07,75\n" +
 204               "2008-05-08,70\n" +
 205               "2008-05-09,80\n"
 206             );
 207           </script>
 208         </div>
 209       </div>
 210
 211       <p style="clear:both">In order to keep this example self-contained, the second parameter is raw CSV data. The dygraphs library parses this data (including column headers), resizes its container to a reasonable default, calculates appropriate axis ranges and tick marks and draws the graph.</p>
 212
 213       <p>In most applications, it makes more sense to include a CSV file instead. If the second parameter to the constructor doesn't contain a newline, 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&amp;monthend=12&amp;yearend=2007&amp;req_city=NA&amp;req_state=NA&amp;req_statename=NA">Weather Underground</a>)</p>
 214
 215       <div class="example" style="clear:both;">
 216         <div class="codeblock" style="float:left;width:400px;">
 217           <h3 style="text-align:center">HTML</h3>
 218           <code>
 219 <pre>
 220 &lt;html&gt;
 221 &lt;head&gt;
 222 &lt;script type=&quot;text/javascript&quot;
 223   src=&quot;dygraph-combined.js&quot;&gt;&lt;/script&gt;
 224 &lt;/head&gt;
 225 &lt;body&gt;
 226 &lt;div id=&quot;graphdiv2&quot;
 227   style=&quot;width:500px; height:300px;&quot;&gt;&lt;/div&gt;
 228 &lt;script type=&quot;text/javascript&quot;&gt;
 229   g2 = new Dygraph(
 230     document.getElementById(&quot;graphdiv2&quot;),
 231     &quot;temperatures.csv&quot;, // path to CSV file
 232     {}          // options
 233   );
 234 &lt;/script&gt;
 235 &lt;/body&gt;
 236 &lt;/html&gt;
 237 </pre>
 238           </code>
 239         </div>
 240         <div class="codeoutput" style="float:left;">
 241           <h3 style="text-align:center">OUTPUT</h3>
 242           <div id="graphdiv2" style="width:500px; height:300px;"></div>
 243           <script type="text/javascript">
 244             g2 = new Dygraph(
 245               document.getElementById("graphdiv2"),
 246               "temperatures.csv",
 247               {}
 248             );
 249           </script>
 250         </div>
 251       </div>
 252
 253       <p style="clear:both;">The file used is <code><a href="temperatures.csv">temperatures.csv</a></code>.</p>
 254
 255       <p>There are a few things to note here:</p>
 256
 257       <ul>
 258         <li>The Dygraph sent off an XHR to get the temperatures.csv file.</li>
 259         <li>The labels were taken from the first line of <code>temperatures.csv</code>, which is <code>Date,High,Low</code>.</li>
 260         <li>The Dygraph automatically chose two different, easily-distinguishable colors for the two data series.</li>
 261         <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>
 262         <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>
 263         <li>The data is very spiky. A moving average would be easier to interpret.</li>
 264       </ul>
 265
 266       <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 <code>rollPeriod</code> option. Here's how it's done:</p>
 267
 268       <div class="example" style="clear:both;">
 269         <div class="codeblock" style="float:left;width:400px;">
 270           <h3 style="text-align:center">HTML</h3>
 271           <code>
 272 <pre>
 273 &lt;html&gt;
 274 &lt;head&gt;
 275 &lt;script type=&quot;text/javascript&quot;
 276   src=&quot;dygraph-combined.js&quot;&gt;&lt;/script&gt;
 277 &lt;/head&gt;
 278 &lt;body&gt;
 279 &lt;div id=&quot;graphdiv3&quot;
 280   style=&quot;width:500px; height:300px;&quot;&gt;&lt;/div&gt;
 281 &lt;script type=&quot;text/javascript&quot;&gt;
 282   g3 = new Dygraph(
 283     document.getElementById(&quot;graphdiv3&quot;),
 284     &quot;temperatures.csv&quot;,
 285     {
 286       rollPeriod: 7,
 287       showRoller: true
 288     }
 289   );
 290 &lt;/script&gt;
 291 &lt;/body&gt;
 292 &lt;/html&gt;
 293 </pre>
 294           </code>
 295         </div>
 296         <div class="codeoutput" style="float:left;">
 297           <h3 style="text-align:center">OUTPUT</h3>
 298           <div id="graphdiv3" style="width:500px; height:300px;"></div>
 299           <script type="text/javascript">
 300             g3 = new Dygraph(
 301               document.getElementById("graphdiv3"),
 302               "temperatures.csv",
 303               {
 304                 rollPeriod: 7,
 305                 showRoller: true
 306               }
 307             );
 308           </script>
 309         </div>
 310       </div>
 311
 312       <p style="clear:both;">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). Also note that we've explicitly set the size of the chart div.</p>
 313
 314       <h2>Error Bars</h2>
 315
 316       <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 <em>&plusmn;n</em> 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. <em>&sigma; = sqrt( (&sigma;<sub>1<sup>2</sup></sub> + &sigma;<sub>2<sup>2</sup></sub> + ... + &sigma;<sub>n<sup>2</sup></sub>) / n )</em></p>
 317
 318       <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 at <a href="twonormals.csv">twonormals.csv</a>.</p>
 319
 320       <div class="example" style="clear:both;">
 321         <div class="codeblock" style="float:left;width:400px;">
 322           <h3 style="text-align:center">HTML</h3>
 323           <code>
 324 <pre>
 325 &lt;html&gt;
 326 &lt;head&gt;
 327 &lt;script type=&quot;text/javascript&quot;
 328   src=&quot;combined.js&quot;&gt;&lt;/script&gt;
 329 &lt;/head&gt;
 330 &lt;body&gt;
 331 &lt;div id=&quot;graphdiv4&quot;
 332   style=&quot;width:480px; height:320px;&quot;&gt;&lt;/div&gt;
 333 &lt;script type=&quot;text/javascript&quot;&gt;
 334   g4 = new Dygraph(
 335     document.getElementById(&quot;graphdiv4&quot;),
 336     &quot;twonormals.csv&quot;,
 337     {
 338       rollPeriod: 7,
 339       showRoller: true,
 340       errorBars: true,
 341       valueRange: [50,125]
 342     }
 343   );
 344 &lt;/script&gt;
 345 &lt;/body&gt;
 346 &lt;/html&gt;
 347 </pre>
 348           </code>
 349         </div>
 350         <div class="codeoutput" style="float:left;">
 351           <h3 style="text-align:center">OUTPUT</h3>
 352           <div id="graphdiv4" style="width:480px; height:320px;"></div>
 353           <script type="text/javascript">
 354             g4 = new Dygraph(
 355               document.getElementById("graphdiv4"),
 356               "twonormals.csv",
 357               {
 358                 rollPeriod: 7,
 359                 showRoller: true,
 360                 errorBars: true,
 361                 valueRange: [50,125]
 362               }
 363             );
 364           </script>
 365         </div>
 366       </div>
 367
 368       <p style="clear:both;">Things to note here:</p>
 369
 370       <ul>
 371         <li>The <strong>errorBars</strong> option affects both the interpretation of the CSV file and the display of the graph. When <strong>errorBars</strong> is set to true, each line is interpreted as <em>YYYYMMDD</em>, <em>A</em>, <em>sigma_A</em>, <em>B</em>, <em>sigma_B</em>, &hellip;</li>
 372         <li>The first line of the CSV file doesn't mention the error columns. In this case, it's just "Date,Series1,Series2".</li>
 373         <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>
 374         <li>The error bars are partially transparent. This can be seen when they overlap one another.</li>
 375       </ul>
 376
 377       <h2 id="ie">Internet Explorer Compatibility</h2>
 378
 379       <p>The dygraphs library relies heavily on the HTML5 <code>&lt;canvas&gt;</code> tag, which Microsoft Internet Explorer did not traditionally support. To use Microsoft's native canvas implementation in IE9, you need to set an HTML5 doctype on your page:</p>
 380
 381 <pre>
 382 &lt;!DOCTYPE html&gt;
 383 </pre>
 384
 385       <p>When IE9 is in HTML5 mode, dygraphs works just like in other modern browsers.</p>
 386
 387       <p>If you want to support previous versions of Internet Explorer (IE6&ndash;IE8), you'll need to include the <a href="http://code.google.com/p/explorercanvas/">excanvas</a> library, which emulates the <code>&lt;canvas&gt;</code> tag using VML. You can add excanvas by including the following snippet:</p>
 388
 389 <pre>
 390 &lt;!DOCTYPE html&gt;
 391 &lt;html&gt;
 392   &lt;head&gt;
 393     &lt;meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7; IE=EmulateIE9"&gt;
 394     &lt;!--[if IE]&gt;&lt;script src="path/to/excanvas.js"&gt;&lt;/script&gt;&lt;![endif]--&gt;
 395   &lt;/head&gt;
 396 </pre>
 397
 398 <p>(This is surprisingly tricky because the HTML5 doctype breaks excanvas in IE8. See <a href="https://groups.google.com/group/dygraphs-users/browse_thread/thread/c60709e04bc7fe5f#">this discussion</a> for details. Note that the &lt;meta http-equiv&hellip;&gt; line must appear <i>first</i> in the &lt;head&gt; section for this to work properly.)</p>
 399
 400     <p>While VML emulation sounds like it would be slow, it works well in practice for most charts.</p>
 401
 402     <p>One common gotcha to look out for: make sure you don't have any trailing commas in parameter lists, e.g.</p>
 403
 404 <pre>
 405 new Dygraph(el, data, {
 406   showRoller: true,  // note trailing comma
 407 })</pre>
 408
 409     <p>Most browsers will ignore the trailing comma, but it will break under IE.</p>
 410
 411     <p>You may also need to delay instantiating any dygraphs until after the DOM
 412     content is ready, as there have been some <a
 413       href="https://groups.google.com/d/topic/dygraphs-users/qPX4Syx2kz8/discussion">reports</a>
 414     that excanvas won't work until this happens. If you're using jQuery, this
 415     means drawing your charts inside of a <code>$(function() { ... })</code>
 416     block.</p>
 417
 418     <h2 id="gviz">GViz Data</h2>
 419
 420     <p>The <a
 421       href="http://code.google.com/apis/visualization/documentation/index.html">Google
 422       Visualization API</a> provides a standard interface for describing data.
 423     Once you've specified your data using this API, you can plug in any
 424     GViz-compatible visualization. dygraphs is such a visualization. In
 425     particular, it can be used as a drop-in replacement for the
 426     AnnotatedTimeline visualization used on Google Finance and other sites. To
 427     see how this works, check out the <a href="tests/annotation-gviz.html">gviz
 428       annotation demo.</a></p>
 429
 430     <p>For a simple demonstration of how to use dygraphs a GViz visualization, see <a href="http://danvk.org/dygraphs/tests/gviz.html">http://danvk.org/dygraphs/tests/gviz.html</a>. dygraphs can also be used as a GViz gadget. This allows it to be embedded inside of a Google Spreadsheet. For a demonstration of this, see <a   href="http://spreadsheets.google.com/ccc?key=0Anx1yCqeL8YUdDR1c3pPREhraGhkWmdhaURjOXRncXc&amp;hl=en">this spreadsheet</a>. The URL for the gadget is <code><a href="http://danvk.org/dygraphs/gadget.xml">http://danvk.org/dygraphs/gadget.xml</a></code>.</p>
 431
 432     <p>Here's an example of a published gviz gadget using dygraphs:</p>
 433
 434     <script src="http://spreadsheets.google.com/gpub?url=http%3A%2F%2Fkb8jbn8l90ocl9n4b14jrcvp61ceqis5.spreadsheets.gmodules.com%2Fgadgets%2Fifr%3Fup__table_query_url%3Dhttp%253A%252F%252Fspreadsheets.google.com%252Ftq%253Frange%253DA1%25253AC31%2526headers%253D-1%2526key%253D0Anx1yCqeL8YUdDR1c3pPREhraGhkWmdhaURjOXRncXc%2526gid%253D0%2526pub%253D1%26up__table_query_refresh_interval%3D300%26url%3Dhttp%253A%252F%252Fdanvk.org%252Fdygraphs%252Fgadget.xml%253Fnocache&height=215&width=530"></script>
 435
 436     <h2 id="baseball">Charting Fractions</h2>
 437
 438     <p>Situations often arise where you want to plot fractions, e.g. the fraction of respondents in a poll who said they'd vote for candidate X or the number of hits divided by at bats (baseball's batting average). Fractions require special treatment for two main reasons:</p>
 439
 440     <ul>
 441       <li>The average of <code>a1/b1</code> and <code>a2/b2</code> is <code>(a1+a2)/(b1+b2)</code>, not <code>(a1/b1 + a2/b2)/2</code>.</li>
 442       <li>The normal approximation is not always applicable and more sophisticated confidence intervals (e.g. the <a href="http://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval">Wilson confidence interval</a>) must be employed to avoid ratios that exceed 100% or go below 0%.</li>
 443     </ul>
 444
 445     <p>Fortunately, dygraphs handles both of these for you! Here's a chart and the command that generated it:</p>
 446
 447     <div style="width:750px; text-align:center; font-weight: bold; font-size: 125%;">Batting Average for Ichiro Suzuki vs. Mariners (2004)</div>
 448     <div id="baseballdiv" style="width:750px; height:300px;"></div>
 449     <script type="text/javascript">
 450       new Dygraph(
 451         document.getElementById("baseballdiv"),
 452         "suzuki-mariners.txt",
 453         {
 454           fractions: true,
 455           errorBars: true,
 456           showRoller: true,
 457           rollPeriod: 15
 458         }
 459       );
 460     </script>
 461
 462     <p>Command:</p>
 463 <pre>
 464   new Dygraph(
 465     document.getElementById(&quot;baseballdiv&quot;),
 466     &quot;suzuki-mariners.txt&quot;,
 467     {
 468       fractions: true,
 469       errorBars: true,
 470       showRoller: true,
 471       rollPeriod: 15
 472     }
 473   );
 474 </pre>
 475
 476     <p>The <code>fractions</code> option indicates that the values in each column should be parsed as fractions (e.g. "1/2" instead of "0.5"). The <code>errorBars</code> option indicates that we'd like to see a confidence interval around each data point. By default, when <code>fractions</code> is set, you get a Wilson confidence interval. If you look carefully at the chart, you can see that the error bars are asymmetric.</p>
 477
 478     <p>A couple things to notice about this chart:</p>
 479
 480     <ul>
 481       <li>The error bars for Ichiro's batting average are larger than for the Mariners', since he has far fewer at bats than his team.</li>
 482       <li>dygraphs makes it easy to see "batting average over the last 30 games". This is ordinarily quite difficult to compute. It makes it clear where the "hot" and "cold" part of Suzuki's season were.</li>
 483       <li>If you set the averaging period to something large, like 200, you'll see the team's and player's batting average through that game. The final number is the overall batting average for the season.</li>
 484       <li>Where the error bars do not overlap, we can say with 95% confidence that the series differ. There is a better than 95% chance that Ichiro was a better hitter than his team as a whole in 2004, the year he won the batting title.</li>
 485     </ul>
 486
 487     <h2 id="stock">One last demo</h2>
 488
 489     <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>
 490
 491     <div id="dow_chart" style="width:750px; height:350px;"></div>
 492     <p><b>Display: </b>
 493     <input type=checkbox id=0 onClick="stockchange(this)" checked>
 494     <label for="0"> Nominal</label>
 495     <input type=checkbox id=1 onClick="stockchange(this)" checked>
 496     <label for="1"> Real</label>
 497     <input type=checkbox id=ann onClick="annotationschange(this)" checked>
 498     <label for="ann"> Annotations</label>
 499     </p>
 500
 501     <script type="text/javascript">
 502       var stock_annotations = [
 503         {
 504           series: "Real",
 505           x: "1929-08-15",
 506           shortText: "A",
 507           text: "1929 Stock Market Peak"
 508         },
 509         {
 510           series: "Nominal",
 511           x: "1987-08-15",
 512           shortText: "B",
 513           text: "1987 Crash"
 514         },
 515         {
 516           series: "Nominal",
 517           x: "1999-12-15",
 518           shortText: "C",
 519           text: "1999 (.com) Peak"
 520         },
 521         {
 522           series: "Nominal",
 523           x: "2007-10-15",
 524           shortText: "D",
 525           text: "All-Time Market Peak"
 526         }
 527       ];
 528
 529     // From http://www.econstats.com/eqty/eq_d_mi_3.csv
 530       stockchart = new Dygraph(
 531         document.getElementById('dow_chart'),
 532         "dow.txt",
 533         {
 534           showRoller: true,
 535           customBars: true,
 536           labelsKMB: true,
 537           drawCallback: function(g, is_initial) {
 538             if (!is_initial) return;
 539             g.setAnnotations( stock_annotations );
 540           }
 541         }
 542       );
 543
 544       function stockchange(el) {
 545         stockchart.setVisibility(el.id, el.checked);
 546       }
 547
 548       function annotationschange(el) {
 549         if (el.checked) {
 550           stockchart.setAnnotations(stock_annotations);
 551         } else {
 552           stockchart.setAnnotations([]);
 553         }
 554       }
 555     </script>
 556 <!--
 557
 558 Here is a script to regenerate the Dow Jones plot:
 559
 560 # Get unadjusted DJIA data in a nice format:
 561 curl -O http://www.econstats.com/eqty/eq_d_mi_3.csv
 562 sed '1,17d' eq_d_mi_3.csv | cut -d, -f1,6 | perl -pe 's/(\d{4}-\d\d)-\d\d/$1/g' | perl -pe 's/, */\t/' | grep -v 'na' | perl -ne 'chomp; ($m,$v) = split/\t/; $close{$m} = $v; if ($low{$m} == 0 || $v < $low{$m}) { $low{$m}=$v } if ($v > $high{$m}) { $high{$m} = $v } END { for $x(sort keys %close) { print "$x\t$low{$x}\t$close{$x}\t$high{$x}\n" } } ' > monthly-djia.tsv
 563
 564 # Fetch and format the CPI data:
 565 curl 'http://data.bls.gov/PDQ/servlet/SurveyOutputServlet?series_id=CUUR0000SA0&years_option=all_years&periods_option=all_periods&output_type=column&output_format=text&delimiter=comma' > cpi-u.txt
 566 sed '1,/Series Id,Year,/d' cpi-u.txt | sed '/^$/,$d' | cut -d, -f2,3,4 | perl -ne 'print if /,M(0[0-9]|1[012]),/' | perl -pe 's/(\d{4}),M(\d{2}),/$1-$2\t/g' > cpi-u.tsv
 567
 568 # Merge:
 569 join -t'     ' cpi-u.tsv monthly-djia.tsv > annotated-djia.tsv
 570 perl -ne 'BEGIN{print "Month,Nominal,Real\n"} chomp; ($m,$cpi,$low,$close,$high) = split /\t/; $cpi /= 100.0; print "$m-15,$low;$close;$high,",($low/$cpi),";",($close/$cpi),";",($high/$cpi),"\n"' annotated-djia.tsv > dow.txt
 571
 572 -->
 573
 574     <h2 id="options">Other Options</h2>
 575
 576     <p>In addition to the options mentioned above (<code>showRoller</code>, <code>rollPeriod</code>, <code>errorBars</code>, <code>valueRange</code>), there are <i>many</i> others.</p>
 577
 578     <p>For a full list, see the <a href="options.html">Dygraphs Options Reference</a> page.</p>
 579
 580     <h2>Common Gotchas</h2>
 581
 582     <p>Here are a few problems that I've frequently run into while using the dygraphs library.</p>
 583
 584     <ul>
 585       <li>If your chart doesn't display, be sure to check your browser's JavaScript error console. dygraphs makes every attempt to log errors and warnings, and these can often guide you in the right direction.</li>
 586       <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>
 587       <li>Make sure your CSV files are in the correct format. They must be of the form <code>YYYYMMDD, series1, series2, </code>&hellip; . And if you set the <code>errorBars</code> property, make sure you alternate data series and standard deviations.</li>
 588       <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 Dygraph, put it inside a table with <code>align = center</code> set.</li>
 589       <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>
 590       <li>Make sure you don't have any trailing commas in your call to the Dygraph constructor or in the options parameter. Firefox, Chrome and Safari ignore these but they can cause a graph to not display in Internet Explorer.</li>
 591     </ul>
 592
 593     <h2 id="gwt">GWT Compatibility</h2>
 594     <p>There is currently no GWT wrapper around Dygraphs, however there is a class that can be used to easily load Dygraphs into the browser.  To use it, include the generated dygraph-gwt.jar file in your classpath and add the following line to your GWT module:</p>
 595
 596 <pre>
 597 &lt;inherits name=&quot;org.danvk.dygraphs&quot;/&gt;
 598 </pre>
 599
 600     <p>Call org.danvk.Dygraphs.install() when your application starts to install the JavaScript code into the browser.  You can use <a href="http://code.google.com/webtoolkit/doc/latest/DevGuideCodingBasicsJSNI.html">JSNI</a> to call Dygraphs from your GWT code, as in the example below.  The example uses the <a href="http://code.google.com/p/gwt-google-apis/wiki/VisualizationGettingStarted">Visualization API for GWT</a> and the <a href="#gviz">Dygraphs GViz API.</a></p>
 601
 602 <pre>
 603 public static native JavaScriptObject drawDygraph(
 604     Element element, DataTable dataTable, double minY, double maxY) /*-{
 605   var chart = new $wnd.Dygraph.GVizChart(element);
 606   chart.draw(dataTable,
 607     {
 608       valueRange: [minY, maxY]
 609     });
 610   return chart;
 611 }-*/;
 612 </pre>
 613
 614     <a name="users" />
 615     <h2>Known Users</h2>
 616     <p>Since its public release in late 2009, dygraphs has found many users
 617     across the web. This is a small collection of the uses that we know about.
 618     If you're using dygraphs, please send <a
 619     href="mailto:dan@dygraphs.com">Dan</a> a link and he'll add it to this
 620     list.</p>
 621
 622     <p>dygraphs was originally developed at Google and has found wide use on
 623     internal dashboards and servers there. There are also a few uses of
 624     dygraphs on public Google products:</p>
 625
 626     <ul class='padded-list'>
 627     <li><a href="http://www.google.com/trends/correlate/search?e=id:20xKcnNqHrk&t=weekly">Google Correlate</a><br/>
 628     <span class="desc">Uses dygraphs for time series visualization. Mostly a standard configuration, with just a few tweaks to match Google style.</span></li>
 629
 630     <li><a href="http://www.google.com/trends/correlate/draw?p=us">Google Correlate - Search by Drawing</a><br/>
 631     <span class="desc">This is a highly customized configuration which lets the user draw a time series. Based on <a href="tests/drawing.html">this demo</a>.</span></li>
 632
 633     <li><a href="https://www.google.com/latitude/b/0/history/manage">Google Latitude History Dashboard</a><br/>
 634     <span class="desc">Uses mouse interaction callbacks to synchronize time series points with markers on a Google Map.</span></li>
 635     </ul>
 636
 637     <p>dygraphs has also found use in other organizations:</p>
 638
 639     <ul class='padded-list'>
 640   <li><a
 641     href="http://iswa.ccmc.gsfc.nasa.gov:8080/IswaSystemWebApp/index.jsp?i_1=388&l_1=99&t_1=316&w_1=800&h_1=400&s_1=0!3!0!ACE.B_x!ACE.B_y!ACE.B_z!">Integrated
 642     Space Weather Analysis System</a> (NASA)<br/>
 643   <span class="desc">&ldquo;We use [dygraphs] in the Integrated Space Weather
 644     Analysis System available from the Space Weather Laboratory at NASA Goddard
 645     Space Flight Center. It works quite well for time series data from various
 646     missions and simulations that we store.&rdquo;</span></li>
 647
 648
 649   <li><a href="http://www.eutelsat.fr">Eutelsat</a><br/>
 650   <span class="desc">&ldquo;Eutelsat uses dygraphs for charting spacecraft
 651     telemetry for a fleet of 25 geostationary satellites. The spacecraft
 652     engineers are very happy with it.  All satellite combined are producing
 653     about 200 millions unique data points per day so we really appreciate the
 654     excellent performance of dygraphs.&rdquo;</span></li>
 655
 656   <li><a href="http://www.10gen.com/mongodb-monitoring-service">10gen MongoDB
 657     Monitoring Service</a><br/>
 658   <span class="desc">A free monitoring service for MongoDB from 10gen (the
 659     creators of MongoDB). Used by thousands of servers and users. Makes use of
 660     <a href="tests/synchronize.html">synchronized charts</a> to display many
 661     quantities simultaneously.</span></li>
 662
 663   <li><a href="http://duckduckgo.com/traffic.html">Duck Duck Go Traffic Dashboard</a><br/>
 664   <span class="desc">DDG uses dygraphs to display a public chart of their daily traffic. They use annotations and the moving average features.</span></li>
 665
 666     <li><a href="http://toolserver.org/~dartar/moodbar/">Wikimedia Foundation - Moodbar data dashboard</a><br/>
 667     <span class="desc">dygraphs is used internally at Wikimedia as a handy solution to monitor the
 668     results of a bunch of small experiments.</span></li>
 669
 670   <li><a href="http://code.google.com/p/quadrant-framework/">quadrant-framework</a> (MySQL Load Testing Framework)<br/>
 671   <span class="desc">A user friendly framework for creating and visualizing
 672     MySQL database load test jobs. For more information on its use of dygraphs,
 673     see <a href="http://themattreid.com/wordpress/2011/05/20/quadrant-framework-rev7-update-adds-dygraphs-support/">this post</a>.</span></li>
 674
 675   <li><a href="http://spinwave.wordpress.com/2011/03/28/spinwave-systems-enables-energy-efficiency-case-studies/">Spinwave Systems</a> (Home energy monitoring)<br/>
 676   <span class="desc">dygraphs is used to chart energy usage over time.</span></li>
 677
 678
 679     <li><a href="http://www.socib.es/jwebchart/?file=http://thredds.socib.es/thredds/dodsC/mooring/weather_station/mobims_calamillor-scb_met001/L1/dep0001_mobims-calamillor_scb-met001_L1_latest.nc">Jwebchart</a><br/>
 680     <span class="desc">
 681     jWebChart is a stand-alone and Thredds' embedded plotting system for
 682     netCDF files. NetCDF is a common standard for the storage and
 683     distribution of scientific data.
 684     </span></li>
 685
 686     <li><a href="http://ngrams.cavorite.com/">n-gramas - Explore las tendencias en los artículos periodísticos de Colombia.</a><br/>
 687
 688
 689     <span class="desc">(English: "Explore trends in newspaper articles of
 690     Colombia"). dygraphs is used for displaying the results of this n-grams
 691     viewer.  Uses an extension for exporting the plots as PNG images
 692     (<a href="http://cavorite.com/labs/js/dygraphs-export/">[1]</a>, <a href="https://github.com/cavorite/dygraphs">[2]</a>).
 693     </span></li>
 694
 695     <li><a href="http://www.glerl.noaa.gov/data/now/wlevels/dbd/altSite.html">NOAA Great Lakes Water Level Dashboard</a><br/>
 696     <span class="desc">The Great Lakes Water Level dashboard was designed to help users view, understand, and compare Great Lakes surface water elevation data and forecasts from a variety of different sources, and across a variety of time scales ranging from monthly average values, to annual and multi-decadal values. First developed in Adobe Flash, a HTML 5 compatible version has been in the works and a functional draft is available here.</span></li>
 697
 698     </ul>
 699
 700     <p>Are you using dygraphs? Please let <a href="mailto:dan@dygraphs.com">Dan</a> know and he'll add your link here!</p>
 701
 702
 703     <h2 id="policy">Data Policy</h2>
 704     <p>dygraphs is purely client-side JavaScript. It does not send your data to any servers &ndash; the data is processed entirely in the client's browser.</p>
 705
 706     <p style="font-size:0.8em">Created May 9, 2008 by <a href=mailto:danvdk@gmail.com>Dan Vanderkam</a></p>
 707   </div>
 708
 709 </body>
 710 </html>