Loop and Conditional Statements

I've got two vectors 1x366 u and v, and I have to make a new 1x366 vector of the arctg of u and v.

But I've got a few conditions depending if the respective value of u and v are negative or positive.

Here's some of the code which I started writing, but I am stuck.

Thank you for any help.

for n = 1:length(u)

if u(n) <0 && v(n) < 0
  atan(v./u); 


elseif u(n) > 0 && v(n) < 0       
   atan(u./v) + 4.712;

    
elseif u(n) < 0 && v(n) > 0 
   atan(u./v) + 1.571;

   
elseif u(n) > 0 && v(n) > 0
    atan(v./u) + 3.142;

end
end

[Scott MacKenzie]

Have you looked at atan2? This is the four-quadrant version of atan -- might be what you need.

[Paulo Eduardo Beiral]

Unfortunately atan2 wont help me in this case, I need exactly the atan with the conditions I entered in my code.

Thank you, mister.

Answer 1

[Steven Lord]

As written your code calls atan at most once per element of u but then throws that result away. You also have magic numbers that look like approximations to multiples of pi.

Instead I recommend using logical indexing.

base1 = atan(v./u);
base2 = atan(u./v);
result = NaN(size(u)); % determine what you want result to be if none of the cases hold

case1 = (u < 0) & (v < 0);
result(case1) = base1(case1);

case2 = (u > 0) & (v < 0);
result(case2) = base2(case2) + (3*pi/2);

% and similar for case3 and case4

[Paulo Eduardo Beiral]

Can't thank you enough!

My best regards!