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Re: Finding all angles within a range of directions; an algorithm question [message #30240]

Mon, 15 April 2002 06:18

Struan Gray
Messages: 178
Registered: December 1995

Senior Member

@yahoo.com writes:

> Could anyone please advise on a better way to do this?

Construct a rotation matrix which describes a rotation of the
original angular coordinates into the 'reference frame' of the plate,
i.e. which translates theta and phi into theta* and phi* where theta*
is the angle from the plate normal.

Then just do a matrix multiply (fast in IDL) and find the items
with theta* less than 90 degrees. You can probably speed it up by not
bothering to calculate phi* at all, and do a matrix multiply with
a vector to just find theta*.

You can either keep track of the time values by suitable identity
elements in the rotation matrix, or seperate out the angular
information and use where/histogram/compare* to find the indices of the
elements you want.

Struan

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[Message index]

		Re: Finding all angles within a range of directions; an algorithm question By: Struan Gray on Mon, 15 April 2002 06:18
		Re: Finding all angles within a range of directions; an algorithm question By: Mark Zimmerman on Thu, 11 April 2002 14:29
		Re: Finding all angles within a range of directions; an algorithm question By: tbowers0 on Tue, 16 April 2002 09:08
		Re: Finding all angles within a range of directions; an algorithm question By: tbowers0 on Tue, 16 April 2002 08:56

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