On Wed, Jul 27, 2011 at 11:24 AM, Tom Arneson <[email protected]> wrote:
> I use *. Which returns length/angle. If you only want the angle just drop
> length.
Yes.
Here's an example use:
atan2=: {:@*.@j.~
haversine=:4 :0
r=. 3959 NB. average radius of earth, in miles
rad=. *&1r180p1
d=. y-x
sin=. 1&o.
cos=. 2&o.
a=. +/(*: sin rad d%2)*1,x *&cos&rad&{. y
r* 2* (atan2&%: -.) a
)
x and y are (latitude,longitude) pairs for two points
The result is the great circle distance, in miles, between those two points.
Hypothetically speaking, I could replace atan2 with the expression
using *. which is its definition, but the concept gets used enough
that I like having a word for it.
--
Raul
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