[GRASSLIST:1666] Re: Using atan function
Glynn Clements
glynn.clements at virgin.net
Tue Nov 4 07:26:50 EST 2003
temiz wrote:
> I want to make sure that using atan function.
> I have two maps containing sin and cosine values in radian.
sine and cosine aren't angles, so they aren't "in radians" (or
anything else).
> Using atan function in r.mapcalc is correct in this way:
> r.mapcalc dene='atan(map_cosine*180/3.14,map_sine*180/3.14)' ?
If you want the result in degrees:
r.mapcalc 'dene=atan(map_cosine,map_sine)'
For radians:
r.mapcalc 'dene=atan(map_cosine,map_sine)*3.14/180'
There is no point scaling the sine/cosine values, although it won't
make any difference as atan(y*k,x*k) == atan(y,x) for all k > 0.
[Aside: does r.mapcalc need a pi() function? Or deg2rad()/rad2deg()
functions? Or, for that matter, anything else?]
--
Glynn Clements <glynn.clements at virgin.net>
More information about the grass-user
mailing list