Hi Andrés,

Yes, a slow rising curve is the mirror image of a fast decaying one. 
However it does not give the mirror image actually if you feed the same 
itype number for both rising and decaying.

I think the original meant perhaps;
If itype > 0, there is a gradually starting, rapidly ending (convex) 
curve, while if itype < 0, the curve is rapidly starting, gradually 
ending (concave).

Kanata Motohashi
http://www3.to/sar/

> I'm not really sure, but the original sounds correct, as a slow rising
> curve is the mirror image of a fast decaying one.