Need to display difference between current month and previous month count in bar chart

[#1]

Hi ,

we have two bar charts

Bar Chart A and Bar Chart B

Bar Chart A display count of employees when date field is selected

Ex:When we select date Mar-2016 Chart A displays previous 3 months counts i.e Mar-16 Feb-16 Jan-16 and their corresponding counts are displayed in Y axis. i.e we show previous 3 months count when we select any month.

Issue :

Chart B should display difference of the count for the two months I .e Present month and its previous month.

Ex:

Please look into the Below image for more details ,

We are using below expression in Chart B:

= fabs(Sum({< DATE ={">=$(=MonthStart(max(DATE),-2))<=$(=MonthEnd(max(DATE), 0))"}>} SOURCE_COUNT)
-
Sum({< DATE ={">=$(=MonthStart(max(DATE),-3))<=$(=MonthEnd(max(DATE), -1))"}>} SOURCE_COUNT )

we are not getting expected output in chart B.Please help and let us  know if any change required in the above expression.

Thanks in advance.

Regards,

Kishore.