[GRASS-user] log(0)-error in r.mapcalculator

[Patrick S.]

Dear List,

I keep getting a log(0) error in r.mapcalculator, even if I enlarge the 
data. This seems to be a bug as I controlled the same data with R and 
get (non-infinity) values. Does r.mapcalculator eventually truncate the 
results of formulas to some integer values?

logit-expression:  log(((A/100)/(1-(A/100)))

To avoid error of log(0) I enlarged the data by 0.00001, 1 and 5 but 
keep getting the error.

I run it out of R with:
param<-list(amap="r_slope_perc", 
formula="log(((A+0.00001)/100)/(1-(A/100))) ", 
outfile="r_slope_perc_logit")
execGRASS("r.mapcalculator", parameters=param, flags=c("overwrite"))

(r.mapcalculator amap="r_slope_perc", 
formula="log(((A+0.00001)/100)/(1-(A/100)))" 
outfile="r_slope_perc_logit" --overwrite)


Any ideas why this happens?

Patrick