log in r.mapcalc

[huddle at Picard.EOS.UoGuelph.Ca]

Hi

In an attempt to overcome a domain error problem encountered while using r.mapcalc's exp(x,y) function I tried to use the log and exp functions together.

	r.mapcalc 'file=if(file.??,log(file.??)'

When I use these funtions I get the message that an overflow has occured during the calculations. I have used an if statement to protect the log from the zero's in the data file and the rest of the data is well within the acceptable range. The values obtained are correct and no strange occurances exist.
In trying to track this down I converted all the zero values to 1 and ran the routine again. No overflow occured. It appears that the presence of the 0 data is not being dealt with by the if statement.

Does anyone have an insight into how r.mapcalc is operating in this reguard?

Steve

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Steve Huddle, Graduate Student
School of Engineering, University of Guelph, Guelph, ON, Canada, N1G 2W1
E-Mail InterNet: HUDDLE at Net2.EOS.UoGuelph.Ca
Telephone: (519) 824-4120 ext 4323                   FAX: (519) 836-0227