docs/tutorial.html

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   3 <style>
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   8
   9 <p>To use dygraphs, include the <code><a href="download.html">dygraph.js</a></code> JavaScript file
  10 and <code>dygraph.css</code> CSS file. Then instantiate a <code>Dygraph</code> object.</p>
  11
  12 <p>Here's a basic example to get things started:</p>
  13
  14 <div class="example" style="clear:both;">
  15   <div class="codeblock" style="float:left;width:400px;">
  16     <h3 style="text-align:center">HTML</h3>
  17   <pre>
  18 &lt;html&gt;
  19 &lt;head&gt;
  20 &lt;script type=&quot;text/javascript&quot;
  21   src=&quot;dygraph.js&quot;&gt;&lt;/script&gt;
  22 &lt;link rel=&quot;stylesheet&quot; src=&quot;dygraph.css&quot; /&gt;
  23 &lt;/head&gt;
  24 &lt;body&gt;
  25 &lt;div id=&quot;graphdiv&quot;&gt;&lt;/div&gt;
  26 &lt;script type=&quot;text/javascript&quot;&gt;
  27   g = new Dygraph(
  28
  29     // containing div
  30     document.getElementById(&quot;graphdiv&quot;),
  31
  32     // CSV or path to a CSV file.
  33     &quot;Date,Temperature\n&quot; +
  34     &quot;2008-05-07,75\n&quot; +
  35     &quot;2008-05-08,70\n&quot; +
  36     &quot;2008-05-09,80\n&quot;
  37
  38   );
  39 &lt;/script&gt;
  40 &lt;/body&gt;
  41 &lt;/html&gt;
  42 </pre>
  43   </div>
  44   <div class="codeoutput" style="float:left;">
  45     <h3 style="text-align:center">OUTPUT</h3>
  46     <div id="graphdiv"></div>
  47     <script type="text/javascript">
  48       g = new Dygraph(
  49
  50         // containing div
  51         document.getElementById("graphdiv"),
  52
  53         // CSV or path to a CSV file.
  54         "Date,Temperature\n" +
  55         "2008-05-07,75\n" +
  56         "2008-05-08,70\n" +
  57         "2008-05-09,80\n"
  58       );
  59     </script>
  60   </div>
  61 </div>
  62
  63 <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>
  64
  65 <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>
  66
  67 <div class="example" style="clear:both;">
  68   <div class="codeblock" style="float:left;width:400px;">
  69     <h3 style="text-align:center">HTML</h3>
  70 <pre>
  71 &lt;html&gt;
  72 &lt;head&gt;
  73 &lt;script type=&quot;text/javascript&quot;
  74   src=&quot;dygraph.js&quot;&gt;&lt;/script&gt;
  75 &lt;link rel=&quot;stylesheet&quot; src=&quot;dygraph.css&quot; /&gt;
  76 &lt;/head&gt;
  77 &lt;body&gt;
  78 &lt;div id=&quot;graphdiv2&quot;
  79   style=&quot;width:500px; height:300px;&quot;&gt;&lt;/div&gt;
  80 &lt;script type=&quot;text/javascript&quot;&gt;
  81   g2 = new Dygraph(
  82     document.getElementById(&quot;graphdiv2&quot;),
  83     &quot;temperatures.csv&quot;, // path to CSV file
  84     {}          // options
  85   );
  86 &lt;/script&gt;
  87 &lt;/body&gt;
  88 &lt;/html&gt;
  89 </pre>
  90   </div>
  91   <div class="codeoutput" style="float:left;">
  92     <h3 style="text-align:center">OUTPUT</h3>
  93     <div id="graphdiv2" style="width:500px; height:300px;"></div>
  94     <script type="text/javascript">
  95       g2 = new Dygraph(
  96         document.getElementById("graphdiv2"),
  97         "temperatures.csv",
  98         {}
  99       );
 100     </script>
 101   </div>
 102 </div>
 103
 104 <p style="clear:both;">The file used is <code><a href="temperatures.csv">temperatures.csv</a></code>.</p>
 105
 106 <p>There are a few things to note here:</p>
 107
 108 <ul>
 109   <li>The Dygraph sent off an XHR to get the temperatures.csv file.</li>
 110   <li>The labels were taken from the first line of <code>temperatures.csv</code>, which is <code>Date,High,Low</code>.</li>
 111   <li>The Dygraph automatically chose two different, easily-distinguishable colors for the two data series.</li>
 112   <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>
 113   <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>
 114   <li>The data is very spiky. A moving average would be easier to interpret.</li>
 115 </ul>
 116
 117 <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>
 118
 119 <div class="example" style="clear:both;">
 120   <div class="codeblock" style="float:left;width:400px;">
 121     <h3 style="text-align:center">HTML</h3>
 122 <pre>
 123 &lt;html&gt;
 124 &lt;head&gt;
 125 &lt;script type=&quot;text/javascript&quot;
 126   src=&quot;dygraph.js&quot;&gt;&lt;/script&gt;
 127 &lt;link rel=&quot;stylesheet&quot; src=&quot;dygraph.css&quot; /&gt;
 128 &lt;/head&gt;
 129 &lt;body&gt;
 130 &lt;div id=&quot;graphdiv3&quot;
 131   style=&quot;width:500px; height:300px;&quot;&gt;&lt;/div&gt;
 132 &lt;script type=&quot;text/javascript&quot;&gt;
 133   g3 = new Dygraph(
 134     document.getElementById(&quot;graphdiv3&quot;),
 135     &quot;temperatures.csv&quot;,
 136     {
 137       rollPeriod: 7,
 138       showRoller: true
 139     }
 140   );
 141 &lt;/script&gt;
 142 &lt;/body&gt;
 143 &lt;/html&gt;
 144 </pre>
 145   </div>
 146   <div class="codeoutput" style="float:left;">
 147     <h3 style="text-align:center">OUTPUT</h3>
 148     <div id="graphdiv3" style="width:500px; height:300px;"></div>
 149     <script type="text/javascript">
 150       g3 = new Dygraph(
 151         document.getElementById("graphdiv3"),
 152         "temperatures.csv",
 153         {
 154           rollPeriod: 7,
 155           showRoller: true
 156         }
 157       );
 158     </script>
 159   </div>
 160 </div>
 161
 162 <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>
 163
 164 <h2>Error Bars</h2>
 165
 166 <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>
 167
 168 <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>
 169
 170 <div class="example" style="clear:both;">
 171   <div class="codeblock" style="float:left;width:400px;">
 172     <h3 style="text-align:center">HTML</h3>
 173 <pre>
 174 &lt;html&gt;
 175 &lt;head&gt;
 176 &lt;script type=&quot;text/javascript&quot;
 177   src=&quot;dygraph.js&quot;&gt;&lt;/script&gt;
 178 &lt;link rel=&quot;stylesheet&quot; src=&quot;dygraph.css&quot; /&gt;
 179 &lt;/head&gt;
 180 &lt;body&gt;
 181 &lt;div id=&quot;graphdiv4&quot;
 182   style=&quot;width:480px; height:320px;&quot;&gt;&lt;/div&gt;
 183 &lt;script type=&quot;text/javascript&quot;&gt;
 184   g4 = new Dygraph(
 185     document.getElementById(&quot;graphdiv4&quot;),
 186     &quot;twonormals.csv&quot;,
 187     {
 188       rollPeriod: 7,
 189       showRoller: true,
 190       errorBars: true,
 191       valueRange: [50,125]
 192     }
 193   );
 194 &lt;/script&gt;
 195 &lt;/body&gt;
 196 &lt;/html&gt;
 197 </pre>
 198 </div>
 199 <div class="codeoutput" style="float:left;">
 200   <h3 style="text-align:center">OUTPUT</h3>
 201   <div id="graphdiv4" style="width:480px; height:320px;"></div>
 202   <script type="text/javascript">
 203     g4 = new Dygraph(
 204       document.getElementById("graphdiv4"),
 205       "twonormals.csv",
 206       {
 207         rollPeriod: 7,
 208         showRoller: true,
 209         errorBars: true,
 210         valueRange: [50,125]
 211       }
 212     );
 213   </script>
 214 </div>
 215 </div>
 216
 217 <p style="clear:both;">Things to note here:</p>
 218
 219 <ul>
 220 <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>
 221 <li>The first line of the CSV file doesn't mention the error columns. In this case, it's just "Date,Series1,Series2".</li>
 222 <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>
 223 <li>The error bars are partially transparent. This can be seen when they overlap one another.</li>
 224 </ul>
 225
 226
 227 <h2 id="gviz">GViz Data</h2>
 228
 229 <p>The <a
 230   href="http://code.google.com/apis/visualization/documentation/index.html">Google
 231   Visualization API</a> provides a standard interface for describing data.
 232 Once you've specified your data using this API, you can plug in any
 233 GViz-compatible visualization. dygraphs is such a visualization. In
 234 particular, it can be used as a drop-in replacement for the
 235 AnnotatedTimeline visualization used on Google Finance and other sites. To
 236 see how this works, check out the <a href="tests/annotation-gviz.html">gviz
 237   annotation demo.</a></p>
 238
 239 <p>Here is another demonstration of
 240 <a href="http://danvk.org/dygraphs/tests/gviz.html">how to use dygraphs a GViz visualization</a>.
 241 </p>
 242
 243 <h2 id="baseball">Charting Fractions</h2>
 244
 245 <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>
 246
 247 <ul>
 248   <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>
 249   <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>
 250 </ul>
 251
 252 <p>Fortunately, dygraphs handles both of these for you! Here's a chart and the command that generated it:</p>
 253
 254 <div style="width:750px; text-align:center; font-weight: bold; font-size: 125%;">Batting Average for Ichiro Suzuki vs. Mariners (2004)</div>
 255 <div id="baseballdiv" style="width:750px; height:300px;"></div>
 256 <script type="text/javascript">
 257   new Dygraph(
 258     document.getElementById("baseballdiv"),
 259     "suzuki-mariners.txt",
 260     {
 261       fractions: true,
 262       errorBars: true,
 263       showRoller: true,
 264       rollPeriod: 15
 265     }
 266   );
 267 </script>
 268
 269 <b>Code:</b>
 270 <pre>
 271 new Dygraph(
 272   document.getElementById(&quot;baseballdiv&quot;),
 273   &quot;suzuki-mariners.txt&quot;,
 274   {
 275     fractions: true,
 276     errorBars: true,
 277     showRoller: true,
 278     rollPeriod: 15
 279   }
 280 );
 281 </pre>
 282
 283 <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>
 284
 285 <p>A couple things to notice about this chart:</p>
 286
 287 <ul>
 288   <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>
 289   <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>
 290   <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>
 291   <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>
 292 </ul>
 293
 294 <h2 id="stock">One last demo</h2>
 295
 296 <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>
 297
 298 <div id="dow_chart" style="width:750px; height:350px;"></div>
 299 <p><b>Display: </b>
 300 <input type=checkbox id=0 onClick="stockchange(this)" checked>
 301 <label for="0"> Nominal</label>
 302 <input type=checkbox id=1 onClick="stockchange(this)" checked>
 303 <label for="1"> Real</label>
 304 <input type=checkbox id=ann onClick="annotationschange(this)" checked>
 305 <label for="ann"> Annotations</label>
 306 </p>
 307
 308 <script type="text/javascript">
 309   var stock_annotations = [
 310     {
 311       series: "Real",
 312       x: "1929-08-15",
 313       shortText: "A",
 314       text: "1929 Stock Market Peak",
 315       cssClass: 'annotation'
 316     },
 317     {
 318       series: "Nominal",
 319       x: "1987-08-15",
 320       shortText: "B",
 321       text: "1987 Crash",
 322       cssClass: 'annotation'
 323     },
 324     {
 325       series: "Nominal",
 326       x: "1999-12-15",
 327       shortText: "C",
 328       text: "1999 (.com) Peak",
 329       cssClass: 'annotation'
 330     },
 331     {
 332       series: "Nominal",
 333       x: "2007-10-15",
 334       shortText: "D",
 335       text: "All-Time Market Peak",
 336       cssClass: 'annotation'
 337     }
 338   ];
 339
 340 // From http://www.econstats.com/eqty/eq_d_mi_3.csv
 341   stockchart = new Dygraph(
 342     document.getElementById('dow_chart'),
 343     "dow.txt",
 344     {
 345       showRoller: true,
 346       customBars: true,
 347       labelsKMB: true,
 348       drawCallback: function(g, is_initial) {
 349         if (!is_initial) return;
 350         g.setAnnotations( stock_annotations );
 351       }
 352     }
 353   );
 354
 355   function stockchange(el) {
 356     stockchart.setVisibility(el.id, el.checked);
 357   }
 358
 359   function annotationschange(el) {
 360     if (el.checked) {
 361       stockchart.setAnnotations(stock_annotations);
 362     } else {
 363       stockchart.setAnnotations([]);
 364     }
 365   }
 366 </script>
 367 <!--
 368
 369 Here is a script to regenerate the Dow Jones plot:
 370
 371 # Get unadjusted DJIA data in a nice format:
 372 curl -O http://www.econstats.com/eqty/eq_d_mi_3.csv
 373 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
 374
 375 # Fetch and format the CPI data:
 376 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
 377 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-$2\t/g' > cpi-u.tsv
 378
 379 # Merge:
 380 join -t'     ' cpi-u.tsv monthly-djia.tsv > annotated-djia.tsv
 381 perl -ne 'BEGIN{print "Month,Nominal,Real\n"} chomp; ($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
 382
 383 -->
 384
 385 <h2>Common Gotchas</h2>
 386
 387 <p>Here are a few problems that I've frequently run into while using the dygraphs library.</p>
 388
 389 <ul>
 390   <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>
 391   <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>
 392   <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>
 393   <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>
 394   <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>
 395   <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>
 396 </ul>
 397
 398 <h2>What next?</h2>
 399
 400 <p>If you need to support Internet Explorer, check out our <a href="ie.html">notes on IE</a>.</p>
 401
 402 <p>To get some inspiration, look at how the <a href="gallery/">charts in our gallery</a> are built.</p>
 403
 404
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