hello everyone,

I have successfully created a pie chart report using iReports, but im facing some problems creating Stacked Bar reports.. I have followed these steps:----

step 1)query:- select first_name as FirstName,last_name as LastName,lead_source as LeadSource,year(date_modified) as "Year" from leads
order by first_name,lead_source,year

step 2) created two group: Year_count and Lead_source count

step3) Created a Stacked bar element.. Right click - > chart properties - >chart data - > details - > add ->
series expression :- $F{LeadSource}
category expression:- $F{Year}
value expression:- $V{Lead_sources_COUNT}

When i click on Execute it gives an error as follows:

Error filling print... Category series name is null.
net.sf.jasperreports.engine.JRRuntimeException: Category series name is null. at net.sf.jasperreports.charts.fill.JRFillCategoryDat aset.customIncrement(JRFillCategoryDataset.java:14 4) at net.sf.jasperreports.engine.fill.JRFillElementData set.increment(JRFillElementDataset.java:169) at net.sf.jasperreports.engine.fill.JRCalculator.calc ulateVariables(JRCalculator.java:152) at net.sf.jasperreports.engine.fill.JRVerticalFiller. fillDetail(JRVerticalFiller.java:682) at net.sf.jasperreports.engine.fill.JRVerticalFiller. fillReportContent(JRVerticalFiller.java:275) at net.sf.jasperreports.engine.fill.JRVerticalFiller. fillReport(JRVerticalFiller.java:117) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill (JRBaseFiller.java:895) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill (JRBaseFiller.java:798) at net.sf.jasperreports.engine.fill.JRFiller.fillRepo rt(JRFiller.java:63) at net.sf.jasperreports.engine.JasperFillManager.fill Report(JasperFillManager.java:402) at net.sf.jasperreports.engine.JasperFillManager.fill Report(JasperFillManager.java:234) at it.businesslogic.ireport.IReportCompiler.run(IRepo rtCompiler.java:947) at java.lang.Thread.run(Unknown Source)
Print was not filled. Try using an EmptyDataSource...


Can anyone guide me in resolving this error..

Thanks in advance