6.22 Adding bands of pattern and color to graphs

As an additional way of emphasizing certain areas of the graph it is possible to add bands (either vertical or horizontal) to any one of the standard X-Y coordinate system based graphs. A band is a rectangular area that stretches one entire axis. This means that if you define a band between X-coordinates 3 and 5 the band area will occupy an area between the X-coordinates and the entire Y-range.

In order to access this functionality you must first make sure that you include the additional library file jpgraph_plotband.php

At the time of this writing (current as of JpGraph 1.8) the table below illustrates the 8 basic types of patterns available. We will shortly show you how you can customize these patterns, To keep these examples clear we have only used one pattern in each figure.

Figure 1: [src]

Figure 2: [src]

Figure 3: [src]

Figure 4: [src]

Figure 5: [src]

Figure 6: [src]

Figure 7: [src]

Figure 8: [src]

To add a one of these patterns to your graph you need to call the method PlotBand::PlotBand() The arguments is fairly easy to understand. The pattern you would like to use is specified by using the correct constant. You can see the name of the correct constants in the figures above. You also need to specify if the band should stretch along the vertical or horizontal axis as well as the min and max coordinates for the band. As coordinates you may also use the special values "min" and "max" which automatically sets the value to the minimum/maximum value of the scale. The specified numeric value will be automatically truncated to fit within the plot area.

We don't discuss the other arguments further here, instead we refer you to the class reference.

6.22.1 Customizing the patterns

All patterns can be customized by

... altering the colors of the band
... altering the density of the patterns using the method PlotBand::SetDensity() The density is specified as an integer in range 1 to 100 where a higher number means a higher density (smaller distance between the lines). For example setting the density of the 3D plane above to 60 gives the result

Figure 9: Increasing the desnity in a pattern [src]
... enabling or disabling a frame around the pattern by using the method PlotBand::ShowFrame() The band will be given the same color as the band.
... finally you can change whether the band should be drawn on top of the plots or beneath, (by default the bands are under the plots), using the PlotBand::SetOrder() as the following example show

Figure 10: Stroking the pattern on top of the plots [src]

Sidenote. 3D planes actually carry another possible modification. You can specify the vanish point to change the perspective used. You can't access the method to change the horizon directly but you can access it through

 $band->prect->SetHorizon($aHorizon)

assuming that the band is a 3D plane.

To finish this section we give one final, more creative, example on how to use the bands.

Figure 11: Combining 3D plane, solid band and a sttaic line [src]

6.23 Adding static lines to the plot

In addition to the bands you can also add static lines to the graph. An example of that is actually shown in figure 11 above. You create a line as an instance of class PlotLine . So for example the lines

 $sline = new
 PlotLine(HORIZONTAL,0,"black",2);

$graph->Add($sline);

will add a 2-pixel wide horizontal static line at Y-position zero.

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