Re-scaling matrix entries to lie within a range

Question

C Meek 2011-11-21

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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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Answer 1

Sven 2011-11-21

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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 2011-11-22

Oops. Yep, you're right of course Walter.. what can I say... I was in a rush? Edited accordingly :)

Walter Roberson 2011-11-22

You need to update your "ans" as well ;-)

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Answer 2

Walter Roberson 2011-11-22

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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)