Accumulated bar plots will show several data series stacked on top of each other in each bar. They are the barplot variant of accumulated area plots as was discussed previously.

An accumulated bar plot is made by aggregating one or more basic bar plots in the container class AccBarPlot as the following code snippet shows

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

<?php
// Some data
$data1y = ...
$data2y = ...
 
// Create two bar plots
$b1plot = new BarPlot($data1y);
$b1plot->SetFillColor('orange');
$b2plot = new BarPlot($data2y);
$b2plot->SetFillColor('blue');
 
// Create the accumulated bar plot
$gbplot = new AccBarPlot(array($b1plot,$b2plot));
 
// Add the accumulated plot to the graph
$graph->Add($gbplot);
?>

An example of an accumulated bar plot is shown in Figure 15.36

Figure 15.36. An accumulated bar plot (example23.php)

There are some subtleties when it comes to the formatting of the frames a round each bar in an accumulated bar plots that might be useful to know. The basic ambiguity that exists is that when we stack the bars on top of each other to create a new accumulated bar each individual bar has properties that was (or could) be set when each individual barplot was created like the frame around the plot.

For example, take the following basic accumulated bar plot (partial script)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

<?php
// Create the first bar
$bplot = new BarPlot($datay1);
$bplot->SetFillGradient('AntiqueWhite2','AntiqueWhite4:0.8',GRAD_VERT);
$bplot->SetColor('darkred');
 
// And the second bar
$bplot2 = new BarPlot($datay2);
$bplot2->SetFillGradient('olivedrab1','olivedrab4',GRAD_VERT);
$bplot2->SetColor('darkgreen');
 
// Join them in an accumulated (stacked) plot
$accbplot = new AccBarPlot(array($bplot,$bplot2));
$graph->Add($accbplot);
?>

As you can see on line 5 and on line 10 we have set the frame color differently in the two individual plots. However, the accumulated bar plot also have a frame color property (and a weight as well) so what shall we use? If we run a full example based on the lines above the result is shown in Figure 15.37 below.

Figure 15.37. Accumulated bar with individual frame colors (accbarframeex01.php)

As can be seen from the graph the bar around each part has the color on th frame that was set on the individual bar. There is one exception though. The line that separates the two bars are shared and will always follow the color of the top bar.

If we instead specify a frame for the accbar by adding the lines

1
2
3
4
5
6

<?php
$accbplot = new AccBarPlot(array($bplot,$bplot2));
$accbplot->SetColor('red');
$accbplot->SetWeight(1);
$graph->Add($accbplot);
?>

The result would be as is shown in Figure 15.38 and the properties of the accumulated bar takes precedence, again with one exception. The divider lines inside the bar is still controlled by the individual plot. By default the line weight on the accumulated bar is 0 which means that it will not be drawn, that is why we have to set a line weight on line 4 above.

Figure 15.38. Accumulated bar with unit frame color (accbarframeex02.php)

If we instead were to set the individual line weight to zero, i.e.

1
2
3
4

<?php
$bplot->SetWeight(0);
$bplot2->SetWeight(0);
?>

and keep the overall frame the result would become as shown in Figure 15.39 below

Figure 15.39. Setting individual frames to weight=0 (accbarframeex03.php)

This uses the same principle as accumulated bar plots but instead of stacking the data series on top of each other they are shown together for the same x-value.

These types of bar graph is used to easy group two or more bars together around each tick (x-value). The bars will be placed immediately beside each other and as a group centered on each tick mark (or between if a text scale is used). A grouped bar is created by aggregating two or more ordinary bar plots and creating a GroupBarPlot

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

<?php
// Some data
$data1y = ...
$data2y = ...
 
// Create the bar plots
$b1plot = new  BarPlot ( $data1y );
$b1plot->SetFillColor ( 'orange' );
 
$b2plot = new  BarPlot ( $data2y );
$b2plot->SetFillColor ( 'blue' );
 
// Create the grouped bar plot
$gbplot = new  GroupBarPlot (array( $b1plot , $b2plot ));
 
// Add it to the graph
$graph->Add ( $gbplot ); 
?>

An example of this is shown in Figure 15.40

Figure 15.40. A grouped bar plot (example21.php)

If the SetWidth() method is used on the GroupBarPlot() it will affect the total width used by all the added plots. Each individual bar width will be the same for all added bars. The default width for grouped bar is 70% of the width between the tick marks in the graph. In Figure 15.41 an example where the width is set to 90% is shown.

Figure 15.41. Adjusting the width of a group bar plot (example22.php)

The number of data points in each data series must be the same. This means that if there are no available values they should be specified as 0. An example of this is shown in Figure 15.42

Figure 15.42. All data series in a grouped bar graph must have the same number of data points (groupbarex1.php)

It is perfectly possible to combine the previous bar types to have a grouped accumulated bar plot. This is done in a similar way by aggregating a number of accumulated plots in a group bar plot. The following code snippte shows how this can be done

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

<?php
// Create all the 4 bar plots
$b1plot = new  BarPlot( $data1y );
$b1plot->SetFillColor( "orange" );
$b2plot = new  BarPlot( $data2y );
$b2plot->SetFillColor( "blue" );
$b3plot = new  BarPlot( $data3y );
$b3plot->SetFillColor( "green" );
$b4plot = new  BarPlot( $data4y );
$b4plot->SetFillColor( "brown" );
 
// Create the accumulated bar plots
$ab1plot = new  AccBarPlot(array( $b1plot , $b2plot ));
$ab2plot = new  AccBarPlot(array( $b3plot , $b4plot ));
 
// Create the grouped bar plot
$gbplot = new  GroupBarPlot(array( $ab1plot , $ab2plot ));
 
// Add the combination to the graph
$graph->Add( $gbplot ); 
?>

An example of this is shown in Figure 15.43 below

Figure 15.43. A grouped accumulated bar graph (example24.php)

If a large number of values to needs to be display in a bar graph it is often better to rotated the bar graph 90 degree so that the bars are horizontal instead. There is no special graph type for this so this is achieved by rotating a standard vertical bar graph 90 degrees, usually with a call to

The orientation of the labels of the axis will be automatically adjusted for bar graphs. A basic example is shown in Figure 15.44 below

Figure 15.44. A basic horizontal bar graph (horizbarex1.php)

The example in Figure 15.45shows how to use multiple lines as labels.

Figure 15.45. Using multiple line labels in a horizontal bar graph (horizbarex4.php)