If z is a vector , what is the difference between angle(z) and atan2(z)

Question

Hassan Abdelazeem 2022-1-12

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评论： Hassan Abdelazeem 2022-1-12

采纳的回答： John D'Errico

If z is a vector z=x+j*y, what is the difference between angle(z) and atan2(z)

becuae when I used angle(x+i*.y) gives a differen results

this is the matlab code

clc

clear

close all

f=50;w=2*pi*f;Tperiod=1/f;Tmax=4*Tperiod;Dt=Tperiod/(6*f);N=(Tmax/Dt)+1;

t0=0.00001;

t=zeros(N,1); Bmx=zeros(N,1); Bmy=zeros(N,1);

thetaB=90;Bmax=1.6;

for k=1:N+1

t(k)=t0+Dt*(k-1);

Bmx(k)=Bmax*sin(w*t(k));

Bmy(k)=Bmax*sin(w*t(k)-(thetaB)*pi/180);

end

z=Bmx+i*Bmy;

figure(1);

plot(z,'k*')

hold on

plot(Bmx,Bmy,'r','LineWidth',2)

figure(2)

P1 = atan2(Bmy,Bmx);

P2=1.6.*(180/pi).*angle(Bmx+i.*Bmy);

P3=1.6.*(180/pi).*angle(z);

hold on

plot(P1,'k*')

plot(P2,'r','LineWidth',2)

plot(P3,'b','LineWidth',2)

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John D'Errico 2022-1-12

You could not possibly have used atan2, becuase atan2 does not work with only one argument.

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Answer 1

John D'Errico 2022-1-12

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编辑：John D'Errico 2022-1-12

在 MATLAB Online 中打开

Perhaps you did not use atan2 properly. Consider this example:

z = [1+i,1-i,-1+i,-1-i];
angle(z)
ans = 1×4
    0.7854   -0.7854    2.3562   -2.3562
atan2(imag(z),real(z))
ans = 1×4
    0.7854   -0.7854    2.3562   -2.3562

If you want the result in degrees, this is not difficult. In fact, with atan2d, it already does the conversion for you to degrees.

angle(z)*180/pi
ans = 1×4
    45   -45   135  -135
atan2d(imag(z),real(z))
ans = 1×4
    45   -45   135  -135

The two functions will be compatible, as long as you use them properly. remember that atan2 is a TWO argument utility. You need to separate out the real and imaginary parts to use atan2 or atan2d.

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Hassan Abdelazeem 2022-1-12

Thnak you indeed for your answer

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Answer 2

Paul 2022-1-12

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编辑：Paul 2022-1-12

atan2() returns the answer in radians. So multiply it by 180/pi as for P2 and P3 (or use atan2d(), though atan2d() might result in small numerical differences). And P1 will also need to be multiplied by 1.6 to match P2 and P3.