Bar graph (y axis % top 20 avg)

[#1]

Hi all

I have a table in the format (below).  Looking to create a stacked bar graph with x-axis as dates and Y axis as percentage (Avg of top 20 (rank)  percentage in green and next 20 in red). Please see attached image.

Area        Value  date

London    90%  01-01-2013

USA        80%  .

Asia        93%  .

Europe    78%  .

Australia  60%  .

Russia     96%  .

.                      .

.                      .

.                      .

[#2]

You need to create the 2 expression: 1 - Tot 20 Avg 2- Other 20 Avg

Then Select Stacked bar in Style.

Please post some sample data

[#3]

Thanks.

What could be the expression.

I tried

Expression1: For top 20: If(Rank(Sum(percentage)<=20),Avg(Percentage))

Expression2: For 20-40 : If(Rank(Sum(percentage)>20) And Rank(Sum(percentage)<=40),Avg(Percentage))

[#4]

Please Post the some sample data so community people will help on the expressions.