Charts from HTML tables - tutorial

JSXGraph is able to read data from HTML tables and display charts. Here it is explained how to do it. First, there is an HTML table showing the results of the German Bundestag elections for some parties from 1949 to 2009.

Wahljahr	1949	1953	1957	1961	1965	1969	1972	1976	1980	1983	1987	1990	1994	1998	2002	2005	2009
CDU	25.2	36.4	39.7	35.8	39.3	36.6	35.2	38.0	34.2	38.2	34.5	36.7	34.2	28.4	29.5	27.8	27.3
CSU	5.8	8.8	10.5	9.6	9.6	9.5	9.7	10.6	10.3	10.6	9.8	7.1	7.3	6.7	9.0	7.4	6.5
SPD	29.2	28.8	31.8	36.2	39.3	42.7	45.8	42.6	42.9	38.2	37.0	33.5	36.4	40.9	38.5	34.2	23.0
FDP	11.9	9.5	7.7	12.8	9.5	5.8	8.4	7.9	10.6	7.0	9.1	11.0	6.9	6.2	7.4	9.8	14.6
Bündnis 90/Die Grünen	-	-	-	-	-	-	-	-	1.5	5.6	8.3	5	7.3	6.7	8.6	8.1	10.7

Then, with some keystrokes the JSXGraph chart from this tables is created.

The code to produce this page

The HTML table is generated by this code:

<table id="mytable" style="border: 1px solid gray;">
<tr>
 <td>Wahljahr</td>
 <td>1949</td>
 <td>1953</td>
 <td>1957</td>
 <td>1961</td>
 <td>1965</td>
 <td>1969</td>
 <td>1972</td>
 <td>1976</td>
 <td>1980</td>
 <td>1983</td>
 <td>1987</td>
 <td>1990</td>
 <td>1994</td>
 <td>1998</td>
 <td>2002</td>
 <td>2005</td>
 <td>2009</td>
</tr>
<tr>
 <td>CDU</td>
 <td>25.2</td>
 <td>36.4</td>
 <td>39.7</td>
 <td>35.8</td>
 <td>39.3</td>
 <td>36.6</td>
 <td>35.2</td> 
 <td>38.0</td>
 <td>34.2</td>
 <td>38.2</td>
 <td>34.5</td>
 <td>36.7</td>
 <td>34.2</td>
 <td>28.4</td>
 <td>29.5</td>
 <td>27.8</td>
 <td>27.3</td> 
</tr>
<tr>
 <td>CSU</td>
 <td>5.8</td>
 <td>8.8</td>
 <td>10.5</td>
 <td>9.6</td>
 <td>9.6</td>
 <td>9.5</td>
 <td>9.7</td> 
 <td>10.6</td>
 <td>10.3</td>
 <td>10.6</td>
 <td>9.8</td>
 <td>7.1</td>
 <td>7.3</td>
 <td>6.7</td>
 <td>9.0</td>
 <td>7.4</td>
 <td>6.5</td> 
</tr>
<tr>
 <td>SPD</td>
 <td>29.2</td>
 <td>28.8</td>
 <td>31.8</td>
 <td>36.2</td>
 <td>39.3</td>
 <td>42.7</td>
 <td>45.8</td> 
 <td>42.6</td>
 <td>42.9</td>
 <td>38.2</td>
 <td>37.0</td>
 <td>33.5</td>
 <td>36.4</td>
 <td>40.9</td>
 <td>38.5</td>
 <td>34.2</td>
 <td>23.0</td>
</tr>
<tr>
 <td>FDP</td>
 <td>11.9</td>
 <td>9.5</td>
 <td>7.7</td>
 <td>12.8</td>
 <td>9.5</td>
 <td>5.8</td>
 <td>8.4</td>
 <td>7.9</td>
 <td>10.6</td>
 <td>7.0</td>
 <td>9.1</td>
 <td>11.0</td>
 <td>6.9</td>
 <td>6.2</td>
 <td>7.4</td>
 <td>9.8</td>
 <td>14.6</td>
</tr>
<tr>
 <td>B&uuml;ndnis 90/Die Gr&uuml;nen</td>
 <td>-</td>
 <td>-</td>
 <td>-</td>
 <td>-</td>
 <td>-</td>
 <td>-</td>
 <td>-</td> 
 <td>-</td>
 <td>1.5</td>
 <td>5.6</td>
 <td>8.3</td>
 <td>5</td>
 <td>7.3</td>
 <td>6.7</td>
 <td>8.6</td>
 <td>8.1</td>
 <td>10.7</td>
</tr>
</table>

  var brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox: [-1, 50, 18, -5], axis: true, grid: false}),
      colors = ['black', '#333333', 'red', 'yellow', 'green'],
      years = [1949, 1953, 1957, 1961, 1965, 1969, 1972, 1976, 1980, 1983, 1987, 1990, 1994, 1998, 2002, 2005, 2009],
      chart = brd.create('chart', ['mytable'], {chartStyle: 'point,line', 
                                                withHeaders: true, colorArray: colors, strokeColor: colors, 
                                                fillColor: colors, highlightFillColor: colors, highlightStrokeColor: colors}),
      brd.highlightInfobox = function(x,y,el) {
            this.infobox.setText('<span style="color:black;font-weight:bold">' + years[Math.round(x)-1] + ': ' + y + ' %</span>');
            this.infobox.rendNode.style.border = 'groove ' + el.visProp['strokeColor'] + ' 2px';
            this.infobox.rendNode.style.padding = '5px';
            this.infobox.rendNode.style.backgroundColor = 'white';
      }