calculation of del-f?

[Chetlen Crossnoe]

Hello,

I need to find a way to calculate del-F (that is, F+ - F-) from a set of
reflections including anomalous data in XPLOR 3.851.  I've tried using
the function friedel that is used in some of the macros, but it doesn't
seem to accept it.  Specifically, I tried:

do amplitude (fcalc = abs(fcalc) - abs(friedel(fcalc)))

Anyone know how to do this?  Please email me at cc691077 at bcm.tmc.edu.

Thanks,

Chetlen Crossnoe