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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.</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             strokeWidth: 3.0
  86           }
  87       );
  88 </script>
  89
  90 <h2>Usage</h2>
  91
  92 <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:
  93
  94 <pre>./generate-combined.sh</pre>
  95
  96 <p>The combined JS file is now in <code>dygraph-combined.js</code>. Here's a basic example to get things started:</p>
  97
  98 <table>
  99   <tr><th>HTML</th>
 100       <td rowspan=2><img src=arrow.gif /></td>
 101       <th>Output</th></tr>
 102 <tr>
 103 <td valign=top><pre>
 104 &lt;html&gt;
 105 &lt;head&gt;
 106 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 107 &lt;/head&gt;
 108 &lt;body&gt;
 109 &lt;div id="graphdiv"&gt;&lt;/div&gt;
 110 &lt;script type="text/javascript"&gt;
 111   g = new Dygraph(
 112         document.getElementById("graphdiv"),  // containing div
 113         "Date,Temperature\n" +                // CSV or path to a CSV file.
 114         "20080507,75\n" +
 115         "20080508,70\n" +
 116         "20080509,80\n",
 117       );
 118 &lt;/script&gt;
 119 &lt;/body&gt;
 120 &lt;/html&gt;
 121 </pre>
 122 </td><td valign=top>
 123   <div id="graphdiv"></div>
 124   <script type="text/javascript">
 125     g = new Dygraph(
 126         document.getElementById("graphdiv"),  // containing div
 127         "Date,Temperature\n" +                // CSV or path to a CSV file.
 128         "20080507,75\n" +
 129         "20080508,70\n" +
 130         "20080509,80\n"
 131       );
 132   </script>
 133 </td></tr></table>
 134
 135 <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>
 136
 137 <table>
 138   <tr><th>HTML</th>
 139       <td rowspan=2><img src=arrow.gif /></td>
 140       <th>Output</th></tr>
 141 <tr>
 142 <td valign=top><pre>
 143 &lt;html&gt;
 144 &lt;head&gt;
 145 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 146 &lt;/head&gt;
 147 &lt;body&gt;
 148 &lt;div id="graphdiv" style="width:600px; height:300px;"&gt;&lt;/div&gt;
 149 &lt;script type="text/javascript"&gt;
 150   g = new Dygraph(
 151         document.getElementById("graphdiv"),
 152         "temperatures.csv",  // path to CSV file
 153         {}                   // additional options
 154       );
 155 &lt;/script&gt;
 156 &lt;/body&gt;
 157 &lt;/html&gt;
 158 </pre>
 159 </td><td valign=top>
 160   <div id="graphdiv2" style="width:600px; height:300px;"></div>
 161   <script type="text/javascript">
 162     g2 = new Dygraph(
 163           document.getElementById("graphdiv2"),
 164           "temperatures.csv", {}
 165         );
 166   </script>
 167 </td></tr></table>
 168
 169 <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>
 170
 171 <ul>
 172   <li>The Dygraph sent off an XHR to get the temperatures.csv file.</li>
 173   <li>The labels were taken from the first line of <code>temperatures.csv</code>, which is <code>Date,High,Low</code>.</li>
 174   <li>The Dygraph automatically chose two different, easily-distinguishable colors for the two data series.</li>
 175   <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>
 176   <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>
 177   <li>The data is very spiky. A moving average would be easier to interpret.</li>
 178 </ul>
 179
 180 <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>
 181
 182 <table>
 183   <tr><th>HTML</th>
 184       <td rowspan=2><img src=arrow.gif /></td>
 185       <th>Output</th></tr>
 186 <tr>
 187 <td valign=top><pre>
 188 &lt;html&gt;
 189 &lt;head&gt;
 190 &lt;script type="text/javascript" src="combined.js"&gt;&lt;/script&gt;
 191 &lt;/head&gt;
 192 &lt;body&gt;
 193 &lt;div id="graphdiv" style="width:600px; height:300px;"&gt;&lt;/div&gt;
 194 &lt;script type="text/javascript"&gt;
 195   g = new Dygraph(
 196         document.getElementById("graphdiv"),
 197         "temperatures.csv",
 198         { rollPeriod: 7,
 199           showRoller: true,
 200         }
 201       );
 202 &lt;/script&gt;
 203 &lt;/body&gt;
 204 &lt;/html&gt;
 205 </pre>
 206 </td><td valign=top>
 207   <div id="graphdiv3" style="width:600px; height:300px;"></div>
 208   <script type="text/javascript">
 209     g3 = new Dygraph(
 210           document.getElementById("graphdiv3"),
 211           "temperatures.csv",
 212           { rollPeriod: 7,
 213             showRoller: true,
 214           }
 215         );
 216   </script>
 217 </td></tr></table>
 218
 219 <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>
 220
 221 <h2>Error Bars</h2>
 222 <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>
 223
 224 <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>
 225
 226 <table>
 227   <tr><th>HTML</th>
 228       <td rowspan=2><img src=arrow.gif /></td>
 229       <th>Output</th></tr>
 230 <tr>
 231 <td valign=top><pre>
 232 &lt;html&gt;
 233 &lt;head&gt;
 234 &lt;script type="text/javascript"
 235   src="combined.js"&gt;&lt;/script&gt;
 236 &lt;/head&gt;
 237 &lt;body&gt;
 238 &lt;div id="graphdiv"
 239  style="width:800px; height:400px;"
 240  &gt;&lt;/div&gt;
 241 &lt;script type="text/javascript"&gt;
 242 $ = document.getElementById;
 243 g = new Dygraph(
 244   $("graphdiv"),
 245   "twonormals.csv",
 246   { rollPeriod: 7,
 247     showRoller: true,
 248     errorBars: true,
 249     valueRange: [50,125]
 250   }
 251 );
 252 &lt;/script&gt;
 253 &lt;/body&gt;
 254 &lt;/html&gt;
 255 </pre>
 256 </td><td valign=top>
 257   <div id="graphdiv4" style="width:800px; height:400px;"></div>
 258   <script type="text/javascript">
 259 $ = document.getElementById;
 260 new Dygraph(
 261   document.getElementById("graphdiv4"),
 262   "twonormals.csv",
 263   { rollPeriod: 14,
 264     showRoller: true,
 265     errorBars: true,
 266     valueRange: [50, 125]
 267   }
 268 );
 269   </script>
 270 </td></tr></table>
 271
 272 <p>Things to note here:</p>
 273 <ul>
 274   <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>
 275   <li>The first line of the CSV file doesn't mention the error columns. In this case, it's just "Date,Series1,Series2".</li>
 276   <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>
 277   <li>The error bars are partially transparent. This can be seen when they overlap one another.</li>
 278 </ul>
 279
 280 <h2>One last demo</h2>
 281
 282 <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>
 283
 284 <div id=dow_chart style="width:1000px; height:400px;"></div>
 285 <script type="text/javascript">
 286   // From http://www.econstats.com/eqty/eq_d_mi_3.csv
 287   dow = new Dygraph(
 288     document.getElementById('dow_chart'),
 289     "dow.txt",
 290     {
 291       showRoller: true,
 292       customBars: true,
 293       labelsKMB: true,
 294       padding: {left:30, right:30, top:5, bottom:5}
 295     });
 296 </script>
 297 <!--
 298
 299 Here is a script to regenerate the Dow Jones plot:
 300
 301 # Get unadjusted DJIA data in a nice format:
 302 curl -O http://www.econstats.com/eqty/eq_d_mi_3.csv
 303 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
 304
 305 # Fetch and format the CPI data:
 306 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
 307 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-$2\t/g' > cpi-u.tsv
 308
 309 # Merge:
 310 join -t'       ' cpi-u.tsv monthly-djia.tsv > annotated-djia.tsv
 311 perl -ne 'BEGIN{print "Month,Nominal,Real\n"} chomp; ($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
 312
 313 -->
 314
 315
 316 <h2>Other Options</h2>
 317 <p>These are the options that can be passed in through the optional third parameter of the Dygraph constructor.</p>
 318
 319 <table class=thinborder width=1000>
 320   <tr><th>Name</th><th>Sample Value</th><th>Description</th></tr>
 321   <tr>
 322     <td><b>rollPeriod</b></td>
 323     <td><code>7</code></td>
 324     <td>Number of days over which to average data. Discussed extensively above.</td>
 325   </tr><tr>
 326     <td><b>showRoller</b></td>
 327     <td><code>true</code></td>
 328     <td>Should the rolling average period text box be shown? Default is false.</td>
 329   </tr><tr>
 330     <td><b>colors</b></td>
 331     <td><code>['red',&nbsp;'#00FF00']</code></td>
 332     <td>List of colors for the data series. These can be of the form "#AABBCC"
 333       or "rgb(255,100,200)" or "yellow", etc. If not specified, equally-spaced
 334       points around a color wheel are used.</td>
 335   </tr><tr>
 336     <td><b>colorSaturation</b></td>
 337     <td><code>1.0</code></td>
 338     <td>If <b>colors</b> is not specified, saturation of the
 339       automatically-generated data series colors. (0.0-1.0, default:
 340       1.0)</td>
 341   </tr><tr>
 342     <td><b>colorValue</b></td>
 343     <td><code>0.5</code></td>
 344     <td>If colors is not specified, value of the data series colors, as in
 345       hue/saturation/value. (0.0-1.0, default 0.5)</td>
 346   </tr><tr>
 347     <td><b>clickCallback</b></td>
 348     <td><code>function(e,date){ alert(date); }</code></td>
 349     <td>A function to call when a data point is clicked. The function should take
 350       two arguments, the event object for the click and the date that was
 351       clicked. (default null)</td>
 352   </tr><tr>
 353     <td><b>errorBars</b></td>
 354     <td><code>false</code></td>
 355     <td>Does the data contain standard deviations? Setting this to true alters
 356       the input format (see above). (default false)</td>
 357   </tr><tr>
 358     <td><b>strokeWidth</b></td>
 359     <td><code>2.0</code></td>
 360     <td>Width of the data lines. This can be used to increase the contrast or
 361       some graphs. (default 1.0)</td>
 362   </tr><tr>
 363     <td><b>dateWindow</b></td>
 364     <td><code>[(new&nbsp;Date('2006-01-01')).valueOf(),<br/>
 365         (new&nbsp;Date()).valueOf()]</code></td>
 366     <td>Initially zoom in on a section of the graph. Is of the form [earliest,
 367       latest], where earliest/latest are millis since epoch.  By default, the
 368       full range of the input is shown.</td>
 369   </tr><tr>
 370     <td><b>valueRange</b></td>
 371     <td><code>[10, 110]</code></td>
 372     <td>Explicitly set the vertical range of the graph to [low, high]. By
 373       default, some clever heuristics are used (see above).</td>
 374   </tr><tr>
 375     <td><b>minTickSize</b></td>
 376     <td><code>1</code</td>
 377     <td>The difference between ticks on the y-axis can be greater than or equal
 378       to this, but no less. If you set it to 1, for instance, you'll never get
 379       nonintegral gaps between ticks.</td>
 380   </tr><tr>
 381     <td><b>labelsSeparateLines</b></td>
 382     <td><code>true</code></td>
 383     <td>Put &lt;br/&gt; between lines in the label string. Often used in
 384       conjunction with <b>labelsDiv</b>. (default false)</td>
 385   </tr><tr>
 386     <td><b>labelsDiv</b></td>
 387     <td><code>document.getElementById('foo')</code></td>
 388     <td>Show data labels in an external div, rather than on the graph. (default
 389       null)</td>
 390   </tr><tr>
 391     <td><b>labelsKMB</b></td>
 392     <td><code>true</code></td>
 393     <td>Show K/M/B for thousands/millions/billions on y-axis (default
 394       false).</td>
 395   </tr>
 396   <tr>
 397     <td><b>padding</b></td>
 398     <td><code>{left:&nbsp;40, right:&nbsp;30,<br/>top:&nbsp;5,
 399         bottom:&nbsp;15}</code></td>
 400     <td>Adds extra pixels of padding around the graph. Sometimes a dygraph
 401       gets clipped by surrounding text (see the Demo at the top of this page).
 402       Setting this property appropriately will fix this problem.</td>
 403   </tr>
 404 </table>
 405
 406 <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>
 407
 408 <h2>Common Gotchas</h2>
 409 <p>Here are a few problems that I've frequently run into while using the
 410 dygraphs library.</p>
 411
 412 <ul>
 413   <li>Make sure your CSV files are readable! If your graph isn't showing up,
 414   the XMLHttpRequest for the CSV file may be failing. You can determine whether
 415   this is the case using tools like <a
 416     href="http://www.getfirebug.com/">Firebug</a>.</li>
 417
 418   <li>Make sure your CSV files are in the correct format. They must be of the
 419   form <code>YYYYMMDD,series1,series2,...</code>. And if you set the
 420   <code>errorBars</code> property, make sure you alternate data series and
 421   standard deviations.</li>
 422
 423   <li>dygraphs are not happy when placed inside a <code>&lt;center&gt;</code>
 424   tag. This applies to the CSS <code>text-align</code> property as well. If you
 425   want to center a Dygraph, put it inside a table with "align=center"
 426   set.</li>
 427
 428   <li>Don't set the <code>dateWindow</code> property to a date. It expects
 429   milliseconds since epoch, which can be obtained from a JavaScript Date
 430   object's valueOf method.</li>
 431 </ul>
 432
 433 <p><font size=-1>Created May 9, 2008 by <a href=mailto:danvdk@gmail.com>Dan Vanderkam</a></font></p>
 434
 435 </body>
 436 </html>