Re-scaling matrix entries to lie within a range

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

Answer 1

[Sven]

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)

[Walter Roberson]

>> mod(0,2*pi)-pi

ans =

-3.14159265358979

I don't think so...

[Sven]

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

[Walter Roberson]

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

Answer 2

[Walter Roberson]

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)

Answer 3

[C Meek]

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?

[Sven]

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.