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Re: Need help writing geology software using cirlces

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  • Subject: [mg29132] Re: [mg29117] Need help writing geology software using cirlces
  • From: "Sherman Reed" <sherman.reed at>
  • Date: Wed, 30 May 2001 23:28:21 -0400 (EDT)
  • References: <>
  • Sender: owner-wri-mathgroup at

I assume all angles are measured in a counter-clockwise direction from the
positive x axis.

Take the average of the angles, then use Mod to find the value from 0 to 360

The attached note shows the results for the examples you provided.
[Contact the author to get this - moderator]

If you are going to use trigometric functions to plot points, etc., then
determining the sign of the function is covered in the trig texts.

Average or Mean is straightforward.  I suspect this is not the complete
answer, but it is a beginning.

Sherman C. Reed
sherman.reed at
----- Original Message -----
From: "Peter Wilson" <peter at>
To: mathgroup at
Subject: [mg29132] [mg29117] Need help writing geology software using cirlces

> I am currently writing a computer program that needs to calculate the
> average angle, given numerous angles in a previous sequence.
> Examples:
> 1) Given the angles, 0° and 45°  the average is definitely 22.5°
> 2) Given 2 angles of 350 and 45, the average should be 17.5 degrees
> (hmmm...Is that right?)
> 3) Given 0 and 180 the average can be considered either 90 or 270
> 4) Given 0, 90, 180 and 270, the average may? be considered 0. In such
> my program will cope fine.
> =============
> Here's my question
> =============
> Q. What formula can I use to find the average angle in a circle, from a
> series of angles?
> i.e.. 0,45,56,135,270,360,2,18... etc.
> Please note that I understand basic trigonometry, but that's about it.
> a computer programmer, not a mathematician.
> I would appreciate any help.  My computer program is currently used in
> Geology to track the course of a river, and to provide a predictive model
> the same river in previous and future years.  It currently works, however
> it's a bit rough and I'm currently looking for refinement algorithms.
> Cheers,
> Pete

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