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  54 <ul>
  55 <li><b>Documentation</b>
  56   <ul>
  57   <li><a href="#demo">Demo</a>
  58   <li><a href="#usage">Usage</a>
  59   <li><a href="#stock">Stock chart</a>
  60   <li><a href="#options">Options Reference</a>
  61   <li><a href="#policy">Data Policy</a>
  62   </ul>
  63
  64 <li><b>Project</b>
  65   <ul>
  66   <li><a href="http://github.com/danvk/dygraphs">Source</a>
  67   <li><a href="http://code.google.com/p/dygraphs/issues/">Issues</a>
  68   <li><a href="http://code.google.com/p/dygraphs/issues/entry">Report Bug</a>
  69   <li><a href="mailto:danvdk [at] gmail">Contact</a>
  70   </ul>
  71
  72
  73 <li><b>Gallery</b>
  74   <ul>
  75   <li><a href="tests/demo.html">Basic Demo</a>
  76   <li><a href="tests/gviz.html">GViz Demo</a>
  77   <li><a href="tests/plotter.html">Equation Plotter</a>
  78   <li><a href="tests/perf.html">Performance Test</a>
  79   <li><a href="tests/perf.html">Fractions</a>
  80
  81   <li><a href="tests/label-div.html">Labels in a DIV</a>
  82   <li><a href="tests/numeric-axis.html">Numeric Axis</a>
  83   <li><a href="tests/draw-points.html">Dotted Points</a>
  84
  85   <li><a href="tests/native-format.html">Native Format</a>
  86   <li><a href="tests/grid_dot.html">Crazy Styles</a>
  87   <li><a href="tests/spacing.html">Tick spacing</a>
  88   <li><a href="tests/callback.html">Callbacks</a>
  89   <li><a href="tests/crosshair.html">Crosshairs</a>
  90   <li><a href="tests/hourly.html">Hourly/Minutely data</a>
  91
  92   <li><a href="tests/isolated-points.html">Isolated Points</a>
  93   <li><a href="tests/missing-data.html">Missing Data</a>
  94
  95   <li><a href="tests/border.html">Bordered chart</a>
  96   <li><a href="tests/custom-bars.html">Custom Bars</a>
  97   <li><a href="tests/customLabel.html">Custom Label Styles</a>
  98   <li><a href="tests/dygraph.html">Minimal Example</a>
  99   <li><a href="tests/negative.html">Negative Numbers</a>
 100   <li><a href="tests/noise.html">Noisy Data</a>
 101   <li><a href="tests/two-series.html">Multiple Series</a>
 102   </ul>
 103 </ul>
 104 </div>
 105
 106 <div id="content">
 107 <p><span style="font-size:28pt;">dygraphs JavaScript Visualization Library</span><br/>
 108 <a href="http://github.com/danvk/dygraphs">http://github.com/danvk/dygraphs</a><br/>
 109 See <a href="tests/">gallery</a> and <a href="http://code.google.com/p/dygraphs/issues/">open issues</a></p>
 110
 111 <p>The dygraphs JavaScript library 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>
 112
 113 <h3>Features</h3>
 114 <ul>
 115   <li>Plots time series without using an external server or Flash</li>
 116   <li>Supports error bands around data series</li>
 117   <li>Displays values on mouseover (this makes it easily discoverable)</li>
 118   <li>Interactive zoom</li>
 119   <li>Adjustable averaging period</li>
 120   <li>Customizable click-through actions</li>
 121   <li>Compatible with the Google Visualization API</li>
 122   <li>Works in Internet Explorer (using excanvas)</li>
 123   <li>Intelligent defaults make it easy to use</li>
 124   <li>Lightweight (45kb) and responsive</li>
 125 </ul>
 126
 127 <a name="demo"><h2>Demo</h2>
 128 <p><font size=-1>(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.)</font></p>
 129 <div id="title" style="width:800px; text-align:center; font-weight: bold; font-size: 125%;">Temperatures in New York vs. San Francisco</div>
 130 <div id="demodiv" style="width:800px; height:320px;"></div>
 131 <script type="text/javascript">
 132   g = new Dygraph(
 133           document.getElementById("demodiv"),
 134           "ny-vs-sf.txt",
 135           {
 136             rollPeriod: 14,
 137             showRoller: true,
 138             customBars: true,
 139             yAxisLabelWidth: 30
 140           }
 141       );
 142 </script>
 143
 144 <p>Some things to notice:</p>
 145 <ul>
 146 <li>There's less seasonal temperature variation in SF than in NY.
 147 <li>The difference is about 15&deg; F for SF vs. 50&deg; F for NY.
 148 <li>The daily data (set rolling period to 1) is quite noisy and hides this conclusion.
 149 <li>Using a 14-day moving average makes it clearer. A 100-day rolling period averages out nearly all the specifics from the data.
 150 <li>There's a gap in the data for SF, when the weather station was down (zoom into October 2007 to see it).
 151 <li>The bands around each point indicate average highs and lows.
 152 <li>There is a <i>lot</i> 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.
 153 </ul>
 154
 155 <p>For more demos, browse the dygraph <a href="tests/">tests</a> directory.</p>
 156
 157 <a name="usage"><h2>Usage</h2>
 158
 159 <p>To use dygraphs, include the <code>dygraph-combined.js</code> JavaScript file and instantiate a <code>Dygraph</code> object.</p>
 160
 161 <p>Here's a basic example to get things started:</p>
 162
 163 <table>
 164   <tr><th>HTML</th>
 165       <td rowspan=2><img src=arrow.gif /></td>
 166       <th>Output</th></tr>
 167 <tr>
 168 <td valign=top><pre>
 169 &lt;html&gt;
 170 &lt;head&gt;
 171 &lt;script type="text/javascript"
 172   src="dygraph-combined.js"&gt;&lt;/script&gt;
 173 &lt;/head&gt;
 174 &lt;body&gt;
 175 &lt;div id="graphdiv"&gt;&lt;/div&gt;
 176 &lt;script type="text/javascript"&gt;
 177   g = new Dygraph(
 178         // containing div
 179         document.getElementById("graphdiv"),
 180         // CSV or path to a CSV file.
 181         "Date,Temperature\n" +
 182         "2008-05-07,75\n" +
 183         "2008-05-08,70\n" +
 184         "2008-05-09,80\n"
 185       );
 186 &lt;/script&gt;
 187 &lt;/body&gt;
 188 &lt;/html&gt;
 189 </pre>
 190 </td><td valign=top>
 191   <div id="graphdiv"></div>
 192 </td></tr></table>
 193
 194 <script type="text/javascript">
 195   g1 = new Dygraph(
 196        document.getElementById("graphdiv"),  // containing div
 197        "Date,Temperature\n" +                // CSV or path to a CSV file.
 198        "2008-05-07,75\n" +
 199        "2008-05-08,70\n" +
 200        "2008-05-09,80\n"
 201      );
 202 </script>
 203
 204 <p>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 the its container to a reasonable default, calculates appropriate axis ranges and tick marks and draws the graph.</p>
 205
 206 <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&monthend=12&yearend=2007&req_city=NA&req_state=NA&req_statename=NA">Weather Underground</a>)</p>
 207
 208 <table>
 209   <tr><th>HTML</th>
 210       <td rowspan=2><img src=arrow.gif /></td>
 211       <th>Output</th></tr>
 212 <tr>
 213 <td valign=top><pre>
 214 &lt;html&gt;
 215 &lt;head&gt;
 216 &lt;script type="text/javascript"
 217   src="dygraph-combined.js"&gt;&lt;/script&gt;
 218 &lt;/head&gt;
 219 &lt;body&gt;
 220 &lt;div id="graphdiv"
 221   style="width:500px; height:300px;"&gt;&lt;/div&gt;
 222 &lt;script type="text/javascript"&gt;
 223   new Dygraph(
 224     document.getElementById("graphdiv"),
 225     "temperatures.csv",  // path to CSV file
 226     {}                   // options
 227   );
 228 &lt;/script&gt;
 229 &lt;/body&gt;
 230 &lt;/html&gt;
 231 </pre>
 232 </td><td valign=top>
 233   <div id="graphdiv2" style="width:500px; height:300px;"></div>
 234 </td></tr></table>
 235
 236 <script type="text/javascript">
 237   g2 = new Dygraph(
 238         document.getElementById("graphdiv2"),
 239         "temperatures.csv", {}
 240       );
 241 </script>
 242
 243 <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>
 244
 245 <ul>
 246   <li>The Dygraph sent off an XHR to get the temperatures.csv file.</li>
 247   <li>The labels were taken from the first line of <code>temperatures.csv</code>, which is <code>Date,High,Low</code>.</li>
 248   <li>The Dygraph automatically chose two different, easily-distinguishable colors for the two data series.</li>
 249   <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>
 250   <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>
 251   <li>The data is very spiky. A moving average would be easier to interpret.</li>
 252 </ul>
 253
 254 <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>
 255
 256 <table>
 257   <tr><th>HTML</th>
 258       <td rowspan=2><img src=arrow.gif /></td>
 259       <th>Output</th></tr>
 260 <tr>
 261 <td valign=top><pre>
 262 &lt;html&gt;
 263 &lt;head&gt;
 264 &lt;script type="text/javascript"
 265   src="dygraph-combined.js"&gt;&lt;/script&gt;
 266 &lt;/head&gt;
 267 &lt;body&gt;
 268 &lt;div id="graphdiv"
 269   style="width:500px; height:300px;"&gt;&lt;/div&gt;
 270 &lt;script type="text/javascript"&gt;
 271   g = new Dygraph(
 272         document.getElementById("graphdiv"),
 273         "temperatures.csv",
 274         { rollPeriod: 7,
 275           showRoller: true,
 276         }
 277       );
 278 &lt;/script&gt;
 279 &lt;/body&gt;
 280 &lt;/html&gt;
 281 </pre>
 282 </td><td valign=top>
 283   <div id="graphdiv3" style="width:500px; height:300px;"></div>
 284 </td></tr></table>
 285
 286 <script type="text/javascript">
 287   g3 = new Dygraph(
 288         document.getElementById("graphdiv3"),
 289         "temperatures.csv",
 290         { rollPeriod: 7,
 291           showRoller: true });
 292 </script>
 293
 294 <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). Also note that we've explicitly set the size of the chart div.</p>
 295
 296 <h2>Error Bars</h2>
 297 <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>
 298
 299 <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>
 300
 301 <table>
 302   <tr><th>HTML</th>
 303       <td rowspan=2><img src=arrow.gif /></td>
 304       <th>Output</th></tr>
 305 <tr>
 306 <td valign=top><pre>
 307 &lt;html&gt;
 308 &lt;head&gt;
 309 &lt;script type="text/javascript"
 310   src="combined.js"&gt;&lt;/script&gt;
 311 &lt;/head&gt;
 312 &lt;body&gt;
 313 &lt;div id="graphdiv"
 314  style="width:600px; height:300px;"
 315  &gt;&lt;/div&gt;
 316 &lt;script type="text/javascript"&gt;
 317 $ = document.getElementById;
 318 g = new Dygraph(
 319   $("graphdiv"),
 320   "twonormals.csv",
 321   { rollPeriod: 7,
 322     showRoller: true,
 323     errorBars: true,
 324     valueRange: [50,125]
 325   }
 326 );
 327 &lt;/script&gt;
 328 &lt;/body&gt;
 329 &lt;/html&gt;
 330 </pre>
 331 </td><td valign=top>
 332   <div id="graphdiv4" style="width:600px; height:300px;"></div>
 333 </td></tr></table>
 334
 335 <script type="text/javascript">
 336 $ = document.getElementById;
 337 new Dygraph(
 338   document.getElementById("graphdiv4"),
 339   "twonormals.csv",
 340   { rollPeriod: 14,
 341     showRoller: true,
 342     errorBars: true,
 343     valueRange: [50, 125]
 344   }
 345 );
 346 </script>
 347
 348 <p>Things to note here:</p>
 349 <ul>
 350   <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>
 351   <li>The first line of the CSV file doesn't mention the error columns. In this case, it's just "Date,Series1,Series2".</li>
 352   <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>
 353   <li>The error bars are partially transparent. This can be seen when they overlap one another.</li>
 354 </ul>
 355
 356 <a name="stock"><h2>One last demo</h2>
 357
 358 <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>
 359
 360 <div id=dow_chart style="width:900px; height:350px;"></div>
 361 <script type="text/javascript">
 362   // From http://www.econstats.com/eqty/eq_d_mi_3.csv
 363   dow = new Dygraph(
 364     document.getElementById('dow_chart'),
 365     "dow.txt",
 366     {
 367       showRoller: true,
 368       customBars: true,
 369       labelsKMB: true });
 370 </script>
 371 <!--
 372
 373 Here is a script to regenerate the Dow Jones plot:
 374
 375 # Get unadjusted DJIA data in a nice format:
 376 curl -O http://www.econstats.com/eqty/eq_d_mi_3.csv
 377 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
 378
 379 # Fetch and format the CPI data:
 380 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
 381 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-$2\t/g' > cpi-u.tsv
 382
 383 # Merge:
 384 join -t'       ' cpi-u.tsv monthly-djia.tsv > annotated-djia.tsv
 385 perl -ne 'BEGIN{print "Month,Nominal,Real\n"} chomp; ($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
 386
 387 -->
 388
 389
 390 <a name="options">
 391 <h2>Other Options</h2>
 392 <p>These are the options that can be passed in through the optional third parameter of the Dygraph constructor. To see demonstrations of many of these options, browse the <a href="tests/">dygraphs tests</a> directory.</p>
 393
 394 <table class=thinborder width=900>
 395   <tr><th>Name</th><th>Sample Value</th><th>Description</th></tr>
 396   <tr>
 397     <td><b>includeZero</b></td>
 398     <td><code>true, false</code></td>
 399     <td>Usually, dygraphs will use the range of the data plus some padding to
 400     set the range of the y-axis. If this option is set, the y-axis will always
 401     include zero, typically as the lowest value. This can be used to avoid
 402     exaggerating the variance in the data.</td>
 403   </tr>
 404
 405   <tr>
 406     <td><b>rollPeriod</b></td>
 407     <td><code>7</code></td>
 408     <td>Number of days over which to average data. Discussed extensively above.</td>
 409   </tr>
 410
 411   <tr>
 412     <td><b>showRoller</b></td>
 413     <td><code>true</code></td>
 414     <td>Should the rolling average period text box be shown? Default is false.</td>
 415   </tr>
 416
 417   <tr>
 418     <td><b>colors</b></td>
 419     <td><code>['red',&nbsp;'#00FF00']</code></td>
 420     <td>List of colors for the data series. These can be of the form "#AABBCC"
 421       or "rgb(255,100,200)" or "yellow", etc. If not specified, equally-spaced
 422       points around a color wheel are used.</td>
 423   </tr>
 424
 425   <tr>
 426     <td><b>colorSaturation</b></td>
 427     <td><code>1.0</code></td>
 428     <td>If <b>colors</b> is not specified, saturation of the
 429       automatically-generated data series colors. (0.0-1.0, default:
 430       1.0)</td>
 431   </tr>
 432
 433   <tr>
 434     <td><b>colorValue</b></td>
 435     <td><code>0.5</code></td>
 436     <td>If colors is not specified, value of the data series colors, as in
 437       hue/saturation/value. (0.0-1.0, default 0.5)</td>
 438   </tr>
 439
 440   <tr>
 441     <td><b>clickCallback</b></td>
 442     <td><code>function(e,date){ alert(date); }</code></td>
 443     <td>A function to call when a data point is clicked. The function should take
 444       two arguments, the event object for the click and the date that was
 445       clicked. (default null)</td>
 446   </tr>
 447
 448   <tr>
 449     <td><b>zoomCallback</b></td>
 450     <td><code>function(minDate,maxDate) {}</code></td>
 451     <td>A function to call when the zoom window is changed (either by zooming
 452     in or out). minDate and maxDate are millis since epoch.</td>
 453   </tr>
 454
 455   <tr>
 456     <td><b>strokeWidth</b></td>
 457     <td><code>2.0</code></td>
 458     <td>Width of the data lines. This can be used to increase the contrast or
 459       some graphs. (default 1.0)</td>
 460   </tr>
 461
 462   <tr>
 463     <td><b>dateWindow</b></td>
 464     <td><code>[Date.parse('2006-01-01'),<br/>
 465         (new&nbsp;Date()).valueOf()]</code></td>
 466     <td>Initially zoom in on a section of the graph. Is of the form [earliest,
 467       latest], where earliest/latest are millis since epoch.  By default, the
 468       full range of the input is shown.</td>
 469   </tr>
 470
 471   <tr>
 472     <td><b>valueRange</b></td>
 473     <td><code>[10, 110]</code></td>
 474     <td>Explicitly set the vertical range of the graph to [low, high]. By
 475       default, some clever heuristics are used (see above).</td>
 476   </tr>
 477
 478   <tr>
 479     <td><b>labelsSeparateLines</b></td>
 480     <td><code>true</code></td>
 481     <td>Put &lt;br/&gt; between lines in the label string. Often used in
 482       conjunction with <b>labelsDiv</b>. (default false)</td>
 483   </tr>
 484
 485   <tr>
 486     <td><b>labelsDiv</b></td>
 487     <td><code>document.getElementById('foo')</code></td>
 488     <td>Show data labels in an external div, rather than on the graph. (default
 489       null)</td>
 490   </tr>
 491
 492   <tr>
 493     <td><b>labelsKMB</b></td>
 494     <td><code>true</code></td>
 495     <td>Show K/M/B for thousands/millions/billions on y-axis (default
 496       false).</td>
 497   </tr>
 498
 499   <tr>
 500     <td><b>labelsDivWidth</b></td>
 501     <td>250</td>
 502     <td>Width (in pixels) of the div which shows information on the
 503     currently-highlighted points.</td>
 504   </tr>
 505
 506   <tr>
 507     <td><b>labelsDivStyles</b></td>
 508     <td>{}</td>
 509     <td>Additional styles to apply to the currently-highlighted points div. For
 510     example, { 'font-weigth': 'bold' } will make the labels bold.</td>
 511   </tr>
 512
 513   <tr>
 514     <td><b>highlightCircleSize</b></td>
 515     <td><code>3</code></td>
 516     <td>Size (in pixels) of the dot drawn over highlighted points (default 3).</td>
 517   </tr>
 518
 519   <tr>
 520     <td><b>drawPoints</b></td>
 521     <td><code>false</code></td>
 522     <td>Draw a small dot at each point, in addition to a line going through
 523     the point. This makes the individual data points easier to see, but can
 524     increase visual clutter in the chart. Default: false</td>
 525   </tr>
 526
 527   <tr>
 528     <td><b>pointSize</b></td>
 529     <td><code>1.0</code></td>
 530     <td>The size of the dot to draw on each point in pixels (see
 531     drawPoints). A dot is always drawn when a point is "isolated", i.e.
 532     there is a missing point on either side of it. This also controls the
 533     size of those dots.</td>
 534   </tr>
 535
 536   <tr>
 537     <td><b>pixelsPerXLabel</b>, <b>pixelsPerYLabel</b></td>
 538     <td>50</td>
 539     <td>Number of pixels to require between each x- and y-label. Larger values
 540     will yield a sparser axis with fewer ticks. Defaults: 60 (x-axis), 30
 541     (y-axis).</td>
 542   </tr>
 543
 544   <tr>
 545     <td><b>xAxisLabelWidth</b>, <b>yAxisLabelWidth</b></td>
 546     <td>50</td>
 547     <td>Width (in pixels) of the x- and y-axis labels.</td>
 548   </tr>
 549
 550   <tr>
 551     <td><b>axisLabelFontSize</b></td>
 552     <td>14</td>
 553     <td>Size of the font (in pixels) to use in the axis labels, both x- and
 554     y-axis.</td>
 555   </tr>
 556
 557   <tr>
 558     <td><b>rightGap</b></td>
 559     <td>5</td>
 560     <td>Number of pixels to leave blank at the right edge of the Dygraph. This
 561     makes it easier to highlight the right-most data point.</td>
 562   </tr>
 563
 564   <tr>
 565     <td><b>errorBars</b></td>
 566     <td><code>false</code></td>
 567     <td>Does the data contain standard deviations? Setting this to true alters
 568       the input format (see above). (default false)</td>
 569   </tr>
 570
 571   <tr>
 572     <td><b>sigma</b></td>
 573     <td>2</td>
 574     <td>When errorBars is set, shade this many standard deviations above/below
 575     each point.</td>
 576   </tr>
 577
 578   <tr>
 579     <td><b>fractions</b></td>
 580     <td>false</td>
 581     <td>When set, attempt to parse each cell in the CSV file as "a/b", where a
 582     and b are integers. The ratio will be plotted. This allows computation of
 583     Wilson confidence intervals (see below).</td>
 584   </tr>
 585
 586   <tr>
 587     <td><b>wilsonInterval</b></td>
 588     <td>true</td>
 589     <td>Use in conjunction with the "fractions" option. Instead of plotting +/-
 590     N standard deviations, dygraphs will compute a Wilson confidence interval
 591     and plot that. This has more reasonable behavior for ratios close to 0 or
 592     1.</td>
 593   </tr>
 594
 595   <tr>
 596     <td><b>customBars</b></td>
 597     <td>false</td>
 598     <td>When set, parse each CSV cell as "low;middle;high". Error bars will be
 599     drawn for each point between low and high, with the series itself going
 600     through middle.</td>
 601   </tr>
 602 </table>
 603
 604 <h2>Common Gotchas</h2>
 605 <p>Here are a few problems that I've frequently run into while using the
 606 dygraphs library.</p>
 607
 608 <ul>
 609   <li>Make sure your CSV files are readable! If your graph isn't showing up,
 610   the XMLHttpRequest for the CSV file may be failing. You can determine whether
 611   this is the case using tools like <a
 612     href="http://www.getfirebug.com/">Firebug</a>.</li>
 613
 614   <li>Make sure your CSV files are in the correct format. They must be of the
 615   form <code>YYYYMMDD,series1,series2,...</code>. And if you set the
 616   <code>errorBars</code> property, make sure you alternate data series and
 617   standard deviations.</li>
 618
 619   <li>dygraphs are not happy when placed inside a <code>&lt;center&gt;</code>
 620   tag. This applies to the CSS <code>text-align</code> property as well. If you
 621   want to center a Dygraph, put it inside a table with "align=center"
 622   set.</li>
 623
 624   <li>Don't set the <code>dateWindow</code> property to a date. It expects
 625   milliseconds since epoch, which can be obtained from a JavaScript Date
 626   object's valueOf method.</li>
 627
 628   <li>Make sure you don't have any trailing commas in your call to the Dygraph
 629   constructor or in the options parameter. Firefox, Chrome and Safari ignore
 630   these but they can cause a graph to not display in Internet Explorer.</li>
 631 </ul>
 632
 633 <a name="policy">
 634 <h2>Data Policy</h2>
 635 <p>dygraphs is purely client-side JavaScript. It does not send your data to any
 636 servers -- the data is processed entirely in the client's browser.</p>
 637
 638 <p><font size=-1>Created May 9, 2008 by <a href=mailto:danvdk@gmail.com>Dan Vanderkam</a></font></p>
 639
 640 </div>
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