How to add a horizontal line to a bar chart?

cjmaloof

Quick question that's been stumping me. I'm displaying some data in a stacked bar chart, where the total height of the stack should be compared to a target value. How can I draw a horizontal line on the chart to represent that target?

Thanks,
Chris

bhanley

Hi,

This is pretty straightforward. On your stacked bar chart (or bar chart for that matter), go to the "Format Chart" tab of the wizard. Click on Y-Series (under the "Chart Area" on the left). Then click on the "Markers" button to add your marker.

I have attached a report design that does this. It uses the sample data base. A yellow line is added to the stacked bar chart.

Good Luck!

cjmaloof

Oh, awesome -- thanks!

I don't suppose there's any way to make the target depend on a report parameter? Even if not, it's still pretty helpful.

bhanley

I do not see a way to bind the target to a parameter. That does sound like a better way to do it though.<br />
<br />
I filed an enhancement request to have it looked at. You can track it here: <br />
<br />
<a class='bbc_url' href='http://ted.birt-exchange.com/show_bug.cgi?id=61'>Redirecting to BIRT Exchange</a>

cjmaloof

Bit of a bruising syntax-wrangling session, but I eventually met Rhino and pieced together enough documentation to come up with the following code for the onRender script of the chart:<br />
<br />
<pre class='_prettyXprint _lang-auto _linenums:0'>
importPackage(Packages.org.eclipse.birt.chart.model.data.impl);
function beforeDrawMarkerLine( axis, markerLine, icsc ) {
target = icsc.getExternalContext().getScriptable().getParameterValue("total_target");
markerLine.setValue(NumberDataElementImpl.create(target));
}</pre>
<br />
which changes the line position at runtime.

bhanley

Very cool. Thanks for sharing the code.

Susmitha

Hi,
is "total_target" in the script is a global variable? I am getting error when I pass dataset variable in the getParameterValue () method. Can you please let me know how can I declare/pass backend table column to the getParameterValue method.

Thanks,
Susmitha.

cjmaloof

total_target is a report parameter. Since icsc.getExternalContext().getScriptable() returns an IReportContext ( see <a class='bbc_url' href='http://www.birt-exchange.org/documentation/BIRT_220/EngineJavadoc/enginescript/api/index.html'>Birt Script API</a>) you could use getGlobalVariable() to get a global variable.<br />
<br />
I'm not sure about computing a marker line from the dataset -- don't know if the data series values are available when the line is drawn. If they are, I guess you could use the afterDataSetFilled event to compute a value and store it in a global variable for use by beforeDrawMarkerLine?

oespinosa

Hi.

I add two lines marks giving them value parameters as it ago?

TTman

how to fix the marker (Target Line). I have added two lines to define min and max values on y-axis. But they are not fixed, they are moving constantly as data changes. Thanks in advance. 

jfranken

To create a fixed line at y=10, add code like the following in the chart's beforeGeneration method:

fixedLine = MarkerLineImpl.create(yAxis, NumberDataElementImpl.create(10));