Wrapping an angle

Where v is a vector between -1 and +1

I say

phi = acos(v); %returns phi varying 0->pi

I have also read: http://en.wikipedia.org/wiki/Inverse_trigonometric_functions#General_solutions and understand that acos is symmetrical in the range [-pi pi]. I merely want to view the transistion across 2pi in one montonic sweep.

I wish to view phi varying between -pi and +pi (as per angle.m returns). ie I wish to see the phase increase from 0% to 100% over the course of a full oscillation, when plotted against time.

When I try

phi2 = wrapToPi(phi);    
or
phi2 = wrapToPi(nancumsum(phi));

where

function a1 = wrapToPi(a0)    
 num2pi = floor(a0/(2*pi) + 0.5);     
 a1 = a0 - num2pi*2*pi; 
 end

I get junk answers.

Can anyone help me out? thanks

Answer 1

[Matlab2010]

phiOut = wrapToPi(nancumsum(abs(diff(phi))));