Re-scaling matrix entries to lie within a range

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C Meek
C Meek 2011-11-21
Hey all,
Basically, I have a matrix containing a wide range of phase angles, but I want to re-scale all these angles to their equivalent values within the range [-pi, pi]. Hence, for example, 1.5*pi will become -0.5*pi.
Would anyone have any tips on how to do this? I'm not looking for a full answer; merely any suggestions that would help me get started would be much appreciated!
Craig

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Sven
Sven 2011-11-21
You can use the "mod" command with modulus 2*pi, then minus pi from the result. For example:
mod(4.5*pi + pi, 2*pi) - pi
ans =
-1.5708
mod(1.5*pi + pi, 2*pi) - pi
ans =
1.5708
(above edited for Walter's amendment)
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Sven
Sven 2011-11-22
Oops. Yep, you're right of course Walter.. what can I say... I was in a rush? Edited accordingly :)

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更多回答（2 个）

Walter Roberson
Walter Roberson 2011-11-22
mod(angle + pi, 2*pi) - pi
Note: this will produce the range semi-open interval [-pi, pi) . The original closed interval [-pi, pi] is ambiguous as to what -pi or pi exactly should map to (as they are the same angle)
C Meek
C Meek 2011-11-22
Thanks, that's is helping me on my way.
However, surely once 1.5*pi has been re-scaled it should be -1.5708, and not +1.5708, or am I missing something?
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Sven
Sven 2011-11-22
Yeah, you're right... original answer was "on the way", but not quite correct. It's updated now in a way that gives correct output.

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