Group the series name in chart not work

[artemis_ai]

hello,
   I am going to build a pie chart in cognos 10.2 to show income for each name, but before that, I need group all names with income less than 1% into one. so I use percentage[income] to get income% for each name, and for those name whose income less than 1% , group and name as "other" , I use data item expression if ([income]>0.01) then ([name]) else ('other')    in chart series and income in categories
  but the final chart not group those income less than 1% to other in series, but still show the individual names and their income% in the chart.
can anybody give me the solution to show the correct pie chart? which is income > =1% shows their name but for those income <1% the chart will group their name as "other" and show their total income?

thanks a lot