angle function in matlab formula

Hi everyone,

I am trying to understand the functionality of angle function of matlab. I am trying to convert my matlab code(which we use for proof of concept) to C++ implementation.

input to angle function - 0.487936206701072 + 0.660466136142335i

output of angle function - 0.934517679414299

I know it must be tan-inverse(img/real) with some other constant.

Please help me with the formula?

Answer 1

[Torsten]

It's all written in the MATLAB documentation of "angle":

Algorithms

angle takes a complex number z = x + iy and uses the atan2 function to compute the angle between the positive x-axis and a ray from the origin to the point (x,y) in the xy-plane.

Here is the "proof":

format long
z = 0.487936206701072 + 0.660466136142335*1i;
angle(z)

ans = 
   0.934517679414299

atan2(imag(z),real(z))

ans = 
   0.934517679414299

[Manu Chaudhary]

So, i am assuming that atan2 means a simple mathematical tan inverse?

[Torsten]

No, not quite.

https://de.mathworks.com/help/matlab/ref/atan2.html

[Manu Chaudhary]

It would be great help if you provide a mathematical formula or a small c/c++ code for it.

[James Tursa]

It is an included function to the standard C++ math library. E.g., here is the C++ code:

#include <cmath>
// some code here to assign real_part and imag_part
result = atan2(imag_part,real_part);

[Torsten]

atan2 is a c++ function.

So make an artificial mex-function that calls the c++ version of atan2 (or whatever you intend to do).

[Manu Chaudhary]

Yes, atan function works in c++ but not atan2.

[Torsten]

https://cplusplus.com/reference/cmath/atan2/