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   3     <title>dygraphs JavaScript Library</title>
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  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 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>
  46   <li>Internet Explorer is poorly supported.</li>
  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>
  54 <div id="status" style="width:200px; font-size:0.8em; padding-top:5px;"></div>
  55 </td>
  56 </tr></table>
  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*(8*i);
  66             r += "," + 10*(250 - 8*i);
  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)"],
  82             padding: {left: 40, right: 30, top: 15, bottom: 15}
  83           }
  84       );
  85 </script>
  86
  87 <h2>Usage</h2>
  88
  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:
  90
  91 <pre>./generate-combined.sh</pre>
  92
  93 <p>The combined JS file is now in <code>dygraph-combined.js</code>. Here's a basic example to get things started:</p>
  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 &lt;html&gt;
 102 &lt;head&gt;
 103 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 104 &lt;/head&gt;
 105 &lt;body&gt;
 106 &lt;div id="graphdiv" style="width:400px; height:300px;"&gt;&lt;/div&gt;
 107 &lt;script type="text/javascript"&gt;
 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 &lt;/script&gt;
 119 &lt;/body&gt;
 120 &lt;/html&gt;
 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 &lt;html&gt;
 147 &lt;head&gt;
 148 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 149 &lt;/head&gt;
 150 &lt;body&gt;
 151 &lt;div id="graphdiv" style="width:600px; height:300px;"&gt;&lt;/div&gt;
 152 &lt;script type="text/javascript"&gt;
 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 &lt;/script&gt;
 160 &lt;/body&gt;
 161 &lt;/html&gt;
 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 &lt;html&gt;
 192 &lt;head&gt;
 193 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 194 &lt;/head&gt;
 195 &lt;body&gt;
 196 &lt;div id="graphdiv" style="width:600px; height:300px;"&gt;&lt;/div&gt;
 197 &lt;script type="text/javascript"&gt;
 198   g = new DateGraph(
 199         document.getElementById("graphdiv"),
 200         "temperatures.csv", null,
 201         { rollPeriod: 7,
 202           showRoller: true,
 203           valueRange: [25, 100]
 204         }
 205       );
 206 &lt;/script&gt;
 207 &lt;/body&gt;
 208 &lt;/html&gt;
 209 </pre>
 210 </td><td valign=top>
 211   <div id="graphdiv3" style="width:600px; height:300px;"></div>
 212   <script type="text/javascript">
 213     g3 = new DateGraph(
 214           document.getElementById("graphdiv3"),
 215           "temperatures.csv", null,
 216           { rollPeriod: 7,
 217             showRoller: true,
 218             valueRange: [25, 100]
 219           }
 220         );
 221   </script>
 222 </td></tr></table>
 223
 224 <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>
 225
 226 <h2>Error Bars</h2>
 227 <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>
 228
 229 <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>
 230
 231 <table>
 232   <tr><th>HTML</th>
 233       <td rowspan=2><img src=arrow.gif /></td>
 234       <th>Output</th></tr>
 235 <tr>
 236 <td valign=top><pre>
 237 &lt;html&gt;
 238 &lt;head&gt;
 239 &lt;script type="text/javascript"
 240   src="combined.js"&gt;&lt;/script&gt;
 241 &lt;/head&gt;
 242 &lt;body&gt;
 243 &lt;div id="graphdiv"
 244  style="width:800px; height:400px;"
 245  &gt;&lt;/div&gt;
 246 &lt;script type="text/javascript"&gt;
 247 $ = document.getElementById;
 248 g = new DateGraph(
 249   $("graphdiv"),
 250   "twonormals.csv",
 251   null,
 252   { rollPeriod: 7,
 253     showRoller: true,
 254     errorBars: true,
 255     valueRange: [50,125]
 256   }
 257 );
 258 &lt;/script&gt;
 259 &lt;/body&gt;
 260 &lt;/html&gt;
 261 </pre>
 262 </td><td valign=top>
 263   <div id="graphdiv4" style="width:800px; height:400px;"></div>
 264   <script type="text/javascript">
 265 $ = document.getElementById;
 266 new DateGraph(
 267   document.getElementById("graphdiv4"),
 268   "twonormals.csv",
 269   null,
 270   { rollPeriod: 14,
 271     showRoller: true,
 272     errorBars: true,
 273     valueRange: [50, 125]
 274   }
 275 );
 276   </script>
 277 </td></tr></table>
 278
 279 <p>Things to note here:</p>
 280 <ul>
 281   <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>
 282   <li>The first line of the CSV file doesn't mention the error columns. In this case, it's just "Date,Series1,Series2".</li>
 283   <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>
 284   <li>The error bars are partially transparent. This can be seen when they overlap one another.</li>
 285 </ul>
 286
 287 <h2>One last demo</h2>
 288
 289 <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>
 290
 291 <div id=dow_chart style="width:1000px; height:400px;"></div>
 292 <script type="text/javascript">
 293   // From http://www.econstats.com/eqty/eq_d_mi_3.csv
 294   dow = new DateGraph(
 295     document.getElementById('dow_chart'),
 296     "dow.txt",
 297     null,
 298     {
 299       showRoller: true,
 300       customBars: true,
 301       labelsKMB: true,
 302       padding: {left:30, right:30, top:5, bottom:5}
 303     });
 304 </script>
 305
 306
 307 <h2>Other Options</h2>
 308 <p>These are the options that can be passed in through the fourth parameter of the DateGraph constructor.</p>
 309
 310 <table class=thinborder width=1000>
 311   <tr><th>Name</th><th>Sample Value</th><th>Description</th></tr>
 312   <tr>
 313     <td><b>rollPeriod</b></td>
 314     <td><code>7</code></td>
 315     <td>Number of days over which to average data. Discussed extensively above.</td>
 316   </tr><tr>
 317     <td><b>showRoller</b></td>
 318     <td><code>true</code></td>
 319     <td>Should the rolling average period text box be shown? Default is false.</td>
 320   </tr><tr>
 321     <td><b>colors</b></td>
 322     <td><code>['red',&nbsp;'#00FF00']</code></td>
 323     <td>List of colors for the data series. These can be of the form "#AABBCC"
 324       or "rgb(255,100,200)" or "yellow", etc. If not specified, equally-spaced
 325       points around a color wheel are used.</td>
 326   </tr><tr>
 327     <td><b>colorSaturation</b></td>
 328     <td><code>1.0</code></td>
 329     <td>If <b>colors</b> is not specified, saturation of the
 330       automatically-generated data series colors. (0.0-1.0, default:
 331       1.0)</td>
 332   </tr><tr>
 333     <td><b>colorValue</b></td>
 334     <td><code>0.5</code></td>
 335     <td>If colors is not specified, value of the data series colors, as in
 336       hue/saturation/value. (0.0-1.0, default 0.5)</td>
 337   </tr><tr>
 338     <td><b>clickCallback</b></td>
 339     <td><code>function(e,date){ alert(date); }</code></td>
 340     <td>A function to call when a data point is clicked. The function should take
 341       two arguments, the event object for the click and the date that was
 342       clicked. (default null)</td>
 343   </tr><tr>
 344     <td><b>errorBars</b></td>
 345     <td><code>false</code></td>
 346     <td>Does the data contain standard deviations? Setting this to true alters
 347       the input format (see above). (default false)</td>
 348   </tr><tr>
 349     <td><b>strokeWidth</b></td>
 350     <td><code>2.0</code></td>
 351     <td>Width of the data lines. This can be used to increase the contrast or
 352       some graphs. (default 1.0)</td>
 353   </tr><tr>
 354     <td><b>dateWindow</b></td>
 355     <td><code>[(new&nbsp;Date('2006-01-01')).valueOf(),<br/>
 356         (new&nbsp;Date()).valueOf()]</code></td>
 357     <td>Initially zoom in on a section of the graph. Is of the form [earliest,
 358       latest], where earliest/latest are millis since epoch.  By default, the
 359       full range of the input is shown.</td>
 360   </tr><tr>
 361     <td><b>valueRange</b></td>
 362     <td><code>[10, 110]</code></td>
 363     <td>Explicitly set the vertical range of the graph to [low, high]. By
 364       default, some clever heuristics are used (see above).</td>
 365   </tr><tr>
 366     <td><b>minTickSize</b></td>
 367     <td><code>1</code</td>
 368     <td>The difference between ticks on the y-axis can be greater than or equal
 369       to this, but no less. If you set it to 1, for instance, you'll never get
 370       nonintegral gaps between ticks.</td>
 371   </tr><tr>
 372     <td><b>labelsSeparateLines</b></td>
 373     <td><code>true</code></td>
 374     <td>Put &lt;br/&gt; between lines in the label string. Often used in
 375       conjunction with <b>labelsDiv</b>. (default false)</td>
 376   </tr><tr>
 377     <td><b>labelsDiv</b></td>
 378     <td><code>document.getElementById('foo')</code></td>
 379     <td>Show data labels in an external div, rather than on the graph. (default
 380       null)</td>
 381   </tr><tr>
 382     <td><b>labelsKMB</b></td>
 383     <td><code>true</code></td>
 384     <td>Show K/M/B for thousands/millions/billions on y-axis (default
 385       false).</td>
 386   </tr>
 387   <tr>
 388     <td><b>padding</b></td>
 389     <td><code>{left:&nbsp;40, right:&nbsp;30,<br/>top:&nbsp;5,
 390         bottom:&nbsp;15}</code></td>
 391     <td>Adds extra pixels of padding around the graph. Sometimes a dygraph
 392       gets clipped by surrounding text (see the Demo at the top of this page).
 393       Setting this property appropriately will fix this problem.</td>
 394   </tr>
 395 </table>
 396
 397 <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>
 398
 399 <h2>Common Gotchas</h2>
 400 <p>Here are a few problems that I've frequently run into while using the
 401 dygraphs library.</p>
 402
 403 <ul>
 404   <li>Make sure your CSV files are readable! If your graph isn't showing up,
 405   the XMLHttpRequest for the CSV file may be failing. You can determine whether
 406   this is the case using tools like <a
 407     href="http://www.getfirebug.com/">Firebug</a>.</li>
 408
 409   <li>Make sure your CSV files are in the correct format. They must be of the
 410   form <code>YYYYMMDD,series1,series2,...</code>. If you're specifying the
 411   names of each data series in the CSV file itself, make sure that you pass
 412   <code>null</code> as the third parameter to the DateGraph constructor to let
 413   the library know that. And if you set the <code>errorBars</code> property,
 414   make sure you alternate data series and standard deviations.</li>
 415
 416   <li>dygraphs are not happy when placed inside a <code>&lt;center&gt;</code>
 417   tag. This applies to the CSS <code>text-align</code> property as well. If you
 418   want to center a DateGraph, put it inside a table with "align=center"
 419   set.</li>
 420
 421   <li>If you specify the <code>colors</code> property or name the data series
 422   using the third parameter of the DateGraph constructor, make sure the number
 423   of data series agree in all places: <code>colors</code>, third parameter and
 424   in each line of the CSV file itself.</li>
 425
 426   <li>Don't set the <code>dateWindow</code> property to a date. It expects
 427   milliseconds since epoch, which can be obtained from a JavaScript Date
 428   object's valueOf method.</li>
 429 </ul>
 430
 431 <p><font size=-1>Created May 9, 2008 by <a href=mailto:danvdk@gmail.com>Dan Vanderkam</a></font></p>
 432
 433 </body>
 434 </html>