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disk arc [message #92934]

Wed, 30 March 2016 09:21

Masoud Afshari
Messages: 1
Registered: March 2016

Junior Member

Dears,
I plot a disk with using dist_circle comand line. Now I want to divide the disk to 8 equal arcs and determine which points are inside each arc.

how can I do this??

thanks

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Re: disk arc [message #92939 is a reply to message #92934]

Wed, 30 March 2016 13:45

wlandsman
Messages: 743
Registered: June 2000

Senior Member

If you have a set of X, Y positions and a center position xc,yc then you can find the angle from the center

ang = atan( x-xc, y-yc)

You can then assign the angles into sectors of size !pi/4

On Wednesday, March 30, 2016 at 12:21:35 PM UTC-4, Masoud Afshari wrote:
> Dears,
> I plot a disk with using dist_circle comand line. Now I want to divide the disk to 8 equal arcs and determine which points are inside each arc.
>
> how can I do this??
>
> thanks

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Re: disk arc [message #92941 is a reply to message #92939]

Wed, 30 March 2016 15:47

wlandsman
Messages: 743
Registered: June 2000

Senior Member

On Wednesday, March 30, 2016 at 4:45:13 PM UTC-4, wlandsman wrote:
> If you have a set of X, Y positions and a center position xc,yc then you can find the angle from the center
>
> ang = atan( x-xc, y-yc)
>
> You can then assign the angles into sectors of size !pi/4
>

I had X and Y reversed

ang = atan( y-yc, x-xc)

http://www.harrisgeospatial.com/docs/ATAN.html

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