MATLAB: Return any angle to (0 to 2pi) range

Question

I have a cetain angle let us say x

and I want matlab to change x to become within 0 and 2pi range

example: if x=3pi

then the new value of x have to be pi

Answer 1

The short answer:

mod(x,2*pi)

The long answer for this particular mod operation, is that if you want to get the same answer for trig calculations for large inputs that MATLAB does, you need to do the mod differently:

atan2(sin(x),cos(x)); % effectively mod(x,2*pi)

E.g.,

>> x = 10
x =
    10
>> y = mod(x,2*pi)
y =
   3.716814692820414
>> sin(x)
ans =
  -0.544021110889370
>> sin(y)
ans =
  -0.544021110889370
>> x = 1e25
x =
     1.000000000000000e+25
>> y = mod(x,2*pi)
y =
     0
>> sin(x)
ans =
  -0.305257800135130
>> sin(y)
ans =
     0
>> z = atan2(sin(x),cos(x))
z =
  -0.310209139287907
>> sin(z)
ans =
  -0.305257800135130

Using the atan2( ) approach to doing the mod(x,2*pi) operation results in effectively the same angle that MATLAB uses for the trig operations.