axis_value_label is an array that overrides the default axis_value labels to display custom text instead. This can also be used to reverse the axis_value (see example below). The axis_value labels are the red labels here:
The first value in axis_value_label overrides the first axis label, the second value in axis_value_label overrides the second axis label, and so on.
To override a value label, place the new text in the corresponding position.
To keep the original value label, place a null in the corresponding position.
To hide a value label, place an empty string in the corresponding position.
To add a multi-line label, break the lines with \r. Example: "Show this in\rtwo lines".
If the axis_value_label holds less values than the number of the axis labels, then the unrepresented labels remain unchanged.
Two Value-Axes
In some cases, it might be necessary to display two value-axes to represent data using two different scales. For example, one chart might show both temperature and wind-speed data. Each requiring a different value-axis with a different scale. In this case, the second value-axis can be added programmatically using the draw function. See the third example below.
Example
<chart>
<!-- override the first label -->
<!-- keep the default second label by using a null -->
<!-- override the third label with a multi-line text -->
<!-- hide the fourth label with an empty string-->
<!-- keep the default fifth label by not representing it -->
<axis_value_label>
<string>label 1</string>
<null/>
<string>third\rlabel</string>
<string></string>
</axis_value_label>
</chart>
This example flips the chart vertically to make it grow from top to bottom.
<chart>
<!-- reverse the data by multiplying all the values by -1 -->
<chart_data>
<row>
<null/>
<string>2007</string>
<string>2008</string>
<string>2009</string>
</row>
<row>
<string>Region A</string>
<number>-20</number>
<number>-75</number>
<number>-85</number>
</row>
<row>
<string>Region B</string>
<number>-40</number>
<number>-25</number>
<number>-105</number>
</row>
</chart_data>
<!-- adjust the axis_value range -->
<axis_value min='-120' max='0' steps='4' mode='trim' />
<!-- adjust the chart's background color -->
<chart_rect negative_color='FFFFFF' negative_alpha='75' />
<!-- override the value-axis labels to make them positive numbers -->
<axis_value_label>
<string>120</string>
<string>90</string>
<string>60</string>
<string>30</string>
<string>0</string>
</axis_value_label>
</chart>
In the following example, the chart's data includes temperature and wind-speed values, requiring two different value-axes with different scales:
10am
11am
12am
1pm
Temperature
50
55
53
48
Wind Speed
15
20
25
40
The task is to display the temperature on a scale from 40 to 60 degrees fahrenheit (represented by the left value-axis), and display the wind speed on a scale from 10 to 50 miles/hour (represented by the right value-axis.) Because a chart can only have one scale, the two scales must first be converted to one. In this case, the function As_Percentage() converts the 40 to 60 temperature scale to a percentage from 0 to 100, and converts the 10 to 50 wind-speed scale to a percentage also from 0 to 100.
<?php
//---------------------------------------------------
//this function converts the chart's data so that both series have the same scale from 0 to 100
//this is a PHP function, but any scripting language can be used to generate the same results
function As_Percentage ( $value, $min, $max ){
return ($value-$min)*100/($max-$min);
}
//---------------------------------------------------
?>
<chart>
<!-- set chart_rect, chart_type, and series_color in preparation for the next steps -->
<chart_rect x='75' y='50' width='250' height='160' />
<chart_type>
<string>column</string>
<string>line</string>
</chart_type>
<series_color>
<color>ff8800</color>
<color>88ff00</color>
</series_color>
<!-- convert the chart's data so that both series have the same scale from 0 to 100 -->
<chart_data>
<row>
<null/>
<string>10am</string>
<string>11am</string>
<string>12am</string>
<string>1pm</string>
</row>
<row>
<string>Temperature</string>
<number><?php echo As_Percentage(50,40,60); ?></number>
<number><?php echo As_Percentage(55,40,60); ?></number>
<number><?php echo As_Percentage(53,40,60); ?></number>
<number><?php echo As_Percentage(48,40,60); ?></number>
</row>
<row>
<string>Wind Speed</string>
<number><?php echo As_Percentage(15,10,50); ?></number>
<number><?php echo As_Percentage(20,10,50); ?></number>
<number><?php echo As_Percentage(25,10,50); ?></number>
<number><?php echo As_Percentage(40,10,50); ?></number>
</row>
</chart_data>
<!-- set the value-axis to a scale from 0 to 100. Make it red to match the temperature series color -->
<axis_value min='0' max='100' color='ff8800' />
<!-- override the text in the value-axis so that it displays values from 40 to 60 instead of 0 to 100 -->
<axis_value_label>
<string>40F</string>
<string>45F</string>
<string>50F</string>
<string>55F</string>
<string>60F</string>
</axis_value_label>
<!-- draw the right value-axis to display values from 10 to 50 -->
<!-- make it green to match the wind-speed series color -->
<!-- use a PHP loop to process all the labels -->
<draw>
<?php
for($i=0;$i<5;$i++){
echo "<text x='327' y='".(203-$i*40)."' color='88ff00'>".(10+$i*10)."m/h</text>";
}
?>
</draw>
</chart>
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