How to Compute Cartesian to Polar If the ThetaZeroLocation on Top ?

Hello, like the title of this question, i need to compute a Cartesian Points to Polar Point if the ThetaZeroLocation is on top.

Im using the code :

r = sqrt(x^2+y^2) %for rho
t = atan(y/x) %for theta

even im using this code :

t = atan2(y/x)

and

[theta,rho] = cart2pol(x,y) 

the answer is still wrong. The value on rho or r is right ( but its has little different ) but the value on t or theta is wrong.

for example the data is

x = -0.00781250;
y = -9.593750000000000

so the real answer is

r = 9.605468750000000
t = 1.801263427734375e+02 %  == 180.126

but i get this if im using the first code

r = 9.5938
t = 1.5700

and with the cart2pol

rho = 9.5938
theta = -1.5716

i get this data pair each other so i know the real value.

The polar graphic that i use is like this :

as you can see the zero theta location is on top and its clockwise. so how do i can compute it ?

NB : im sorry if my english is bad

Answer 1

[Matt J]

x = -0.00781250;
y = -9.593750000000000;

t = 90-atan2d(y,x) %for theta

t = 180.0467

[Zaidan Adenin Said]

is this code for all the quadrant ?

when i try this

x = -19.7187500000000;
y = 0.0781250000000000;

the real theta must

t = 270.241699218750

but with using that program

t = 90-atan2d(y,x)

i got

t = -89.7730

#NB : sorry if my response is so late. i cannot acces internet all the time

[Matt J]

t = -89.7730 and t = 270.241699218750 differ by 360 degrees. In other words, they are the same angle.

[Zaidan Adenin Said]

Oh i see. Thats right. Thanks a lot for the code Mr. Matt