The x and y axis each in a graph has an associated scale, labels, titles, grid lines, colors and position. The axis properties are accessed as objects of the axis instance variables in the main graph class. The axis can be access vi the following instance variables.

In addition the library also supports the use of multiple y-axis and they are accessed via an instance array

All axis in turn are instances of class Axis and hence share common properties. The only two property that can be publicly accessed on the axis are

On the other hand there are a large amount of methods that can be used on the axis to adjust various properties. Some examples of commonly used methods are given below. The full description of each method is given in the API reference.

The above methods are valid for all possible axis. So for example the following line sets the font for the labels on the x-axis

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$graph->xaxis->SetFont(FF_ARIAL,FS_NORMAL,12);

and the follwing code set the font for the y-axis

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$graph->yaxis->SetFont(FF_ARIAL,FS_NORMAL,12);

The two major ways to adjust the look and feel of the axis are adjustments of the color and the weight (i.e. width) and this can be done with the appropriate methods as described above.

Grid lines will make it easier to see where the data points are in the graph. The grid lines are access by the properties "xgrid" and "ygrid"of the Graph class. By default only the y-axis grid are enabled by default. The following code example enables the major grids for both the x- and y-axis.

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$graph_>xgrid->Show();
$graph->ygrid->Show();

The grid lines are instances of Class Grid. and supports the following methods

The last method needs an explanation. The fill refers to the possibility to fill the space between the grid lines with alternating colors as specified in the method call. Figure 14.2 shows an example on how this can be used to make it easier to read a plot.

Figure 14.2. Using alternating fill colors in the grid (filledgridex1.php)

In the above example we have also used the possibility of using alpha-blending (for example on the shadow on the legend box).

The example below shows how to use different styles for the major and minor grid lines

Figure 14.3. Using different grid styles for major and minor grids (gridstylesex1.php)

In order to make it easier to setup a couple of typical axis configuration used in science plots there are four predefined configurations as shown in Figure 14.4.

Figure 14.4. Predefined scientific axis positions

AXSTYLE_BOXOUT	AXSTYLE_BOXIN	AXSTYLE_YBOXIN	AXSTYLE_YBOXOUT

The styles can easily be setup with a call to the method

An example of using this setup of the axis is shown in Figure 14.5

Figure 14.5. Example of AXSTYLE_BOXIN axis style (funcex2.php)

The axis can be manually positioned with a call to

Axis::SetPos($aPos)

The argument $aPos is normally the coordinate position on the "other" axis where the crossing of this and the other axis should be. There are also two special positions which are given as strings. They are 'min' and 'max'. Not surprisingly these special positions will always refer to the min and max scale value of the other axis.

The position given is the scale position on the "other"axis, i.e. for the x-axis the position specifies the crossing of the y-axis and vice versa.

Since it is possible to manually specify all aspects of the axis the table below shows some typical common setups and the principle calls needed to achieve the illustrated affect.

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$graph->SetAxisStyle(AXSTYLE_SIMPLE);

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$graph->xaxis->SetPos('max');
$graph->xaxis->SetLabelSide(SIDE_UP);
$graph->xaxis->SetTickSide(SIDE_DOWN);

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$graph->SetAxisStyle(AXSTYLE_SIMPLE);
$graph->SetBox();

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$graph->xaxis->SetPos('max');
$graph->xaxis->SetLabelSide(SIDE_UP);
$graph->xaxis->SetTickSide(SIDE_DOWN);
$graph->SetBox();

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$graph->xaxis->SetPos(0);
$graph->yaxis->SetPos(0);

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$graph->xaxis->SetPos(0);
$graph->yaxis->SetPos(0);
$graph->SetBox();