I have what should be a simple problem. I have a stacked bar chart and my category expression is $F{DATE} and that works just fine. I also have a customizer that prints only every 3rd tick label. This also works just fine. However, when displaying the tick label I want to concatenate the rownumber to the category expression in the form DATE + {N} where N is the count, for example the first bar should be 20130910 {1}, second should be 20130911 {2} etc. Changing the category expression to $F{DATE} + " {" + $F{ROWNUM} + "}" results in some really strange behavior (ROWNUM is explicity selected in my query). What I get is two sets of categories repeated one after the other, one with just the date and one with the concatenated values. In addition the first set of values is processed and spaced out by the customizer while the second set of values is not. Any ideas of what exactly is going on? In my customizer I am geting the domainAxis of the categoryPlot, iterating through the categories and setting the tick label paint to while for all but the 3rd values. In addition if you look at the values with the concatenation of the { } you will see that they are all the values in the first set EACH repeated 4 times which is really bizzare. This stacked bar chart has 2 series and I have set the category expression of both to the same thing - $F{DATE} + " {" + $F{ROWNUM} + "}" Attached images: cap1 - original chart cap2 - after the category expression is set to $F{DATE} + " {" + $F{ROWNUM} + "}"