Area charts. Desire more gradual inclines and declines as in Cognos 8

[pimogo]

Hi. Moving to Cognos 10 from 8 has its little frustrations... the issue now is that when I graph an area chart I notice that it attempts to graph only the months were data exists. The problem with this is that if no data exists for the months before and after, no area is shown as there are no end points to plot. THis also creates cliff-like edge that just drop (see attached pic). I'd prefer gradual drops that taper off.

What setting must one use to return to getting area charts that behave more like they would in Cognos 8?

Many thanks!

[pimogo]

No one else has encountered this?