XQuery/Google Chart Bullet Bar
< XQuery
Motivation edit
To display a Bullet Chart to display the current value of a system parameter with its safe and danger ranges.
Bullet Bars edit
This is one of the chart types supported by the now deprecated " Google Chart API which constructs the chart from URL parameters.
Sample URL edit
http://chart.apis.google.com/chart?cht=bhs&chs=150x30&chd=t:70&chm=r,ff0000,0,0.0,0.5%7Cr,ffff00,0,0.5,0.75%7Cr,00A000,0,0.75,1.0%7Cr,000000,0,0.8,0.81&chco=000000&chbh=10
Sample Screen Image edit
Declarative XML Representation edit
An XML representation of the chart design might be:
<chart >
<type>bar-gauge</type>
<height>30</height> <!-- in pixels -->
<width>150</width> <!-- in pixels -->
<danger-threshold>50</danger-threshold> <!-- end of danger level -->
<danger-color>ff0000</danger-color>
<warning-threshold>75</warning-threshold> <!-- end of warning level -->
<warning-color>ffff00</warning-color>
<ok-threshold>100</ok-threshold> <!-- end of ok level -->
<ok-color>00ff00</ok-color>
<target-value>90</target-value>
</chart>
Google Chars Representation edit
Which, when supplied with a current value, must be transformed into the following URL:
http://chart.apis.google.com/chart?
cht=bhs&
chs=150x30&
chd=t:70&
chm=r,ff0000,0,0.0,0.5|
r,ffff00,0,0.5,0.75|
r,00A000,0,0.75,1.0|
r,000000,0,0.8,0.81&
chco=000000&chbh=10
Sample XQuery Function edit
This function takes the specification of the chart and the current value, and generates the corresponding Google Chart URL.
Note that the width of the danger, warn and ok bars (red, yellow and green) are expressed as a percentage digit from 0 to 100.
declare function local:bullet-bar($spec,$current-value) {
let $danger-width-percent := $spec/danger-threshold div 100
let $warn-width-percent := $spec/warning-threshold div 100
let $ok-width-percent := $spec/ok-threshold div 100
let $target-width-percent := $spec/target-value div 100
let $target-plus-one := $target-width-percent + 0.01
return concat(
'http://chart.apis.google.com/chart?cht=bhs&chs=',
$spec/width,
'x',
$spec/height,
'&chd=t:',$current-value,
'&chm=r,',$spec/danger-color,',0,0.0,', $danger-width-percent,
'|r,',$spec/warning-color,',0,', $danger-width-percent, ',', $warn-width-percent,
'|r,',$spec/ok-color,',0,', $warn-width-percent, ',', $ok-width-percent,
'|r,000000,0,', $target-width-percent, ',', $target-plus-one,
'&chco=000000&chbh=',
round($spec/height * 0.6)
)
};
Generating a bullet bar edit
let $current-value := 70
let $url := local:bullet-bar($bar-spec,$current-value)
return
<div>
<h2>Example bullet bar</h2>
<div> <img src="{$url}"/></div>
</div>