why does the figure doesnt show the two vectors?

Question

shamma aljaberi 2023-11-2

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https://ww2.mathworks.cn/matlabcentral/answers/2041986-why-does-the-figure-doesnt-show-the-two-vectors

评论： dpb 2023-11-2

Hi! i am working on a project using the while loop (similar to my question regarding for loop) the figure doesnt show the plot as desired. what is wrong regarding the code?

code below:

%Links length

L1=5; L2=1; L3=5; L4=7; AP=5;

% ternary link angle (degree)

delta=50;

th2= 0:1.2:360;

range_th2=300;

RP=zeros(1,range_th2);

RA=zeros(1,range_th2);

i=1;

while i<=301

% the loop variables

R1=L1;

R2=L2*(cos(th2(i))+sin(th2(i))*1i);

Z=R1-R2;

Zconj=conj(Z);

% Quadratic equation parameters

a=L4.*Zconj;

b=Z.*Zconj+L4.^2-L3.^2;

c=L4*Z;

T=roots([a b c]);

T_pos=T(2);

%T_pos=(-b+sqrt(b.^2-4.*c.*a))/(2.*a);

S=(L4*T_pos+Z)/L4;

% solution

th3(i)=rad2deg(angle(T_pos));

th4(i)=rad2deg(angle(S));

R3=L3*(cos(th3(i))+sin(th3(i))*1i);

R4=L4*(cos(th4(i))+sin(th4(i))*1i);

thAP=th3(i)-delta;

RAP=AP*(cos(thAP)+sin(thAP)*1i);

%position of A and P

RA(i)=R2;

RP(i)=R2+RAP;

i=i+1;

end

A_real=real(RA)

A_real = 1×301

1.0000 0.3624 -0.7374 -0.8968 0.0875 0.9602 0.6084 -0.5193 -0.9847 -0.1943 0.8439 0.8059 -0.2598 -0.9942 -0.4607 0.6603 0.9392 0.0204 -0.9245 -0.6903 0.4242 0.9977 0.2989 -0.7811 -0.8650 0.1543 0.9768 0.5536 -0.5756 -0.9707

A_imag=imag(RA)

A_imag = 1×301

0 0.9320 0.6755 -0.4425 -0.9962 -0.2794 0.7937 0.8546 -0.1743 -0.9809 -0.5366 0.5921 0.9657 0.1078 -0.8876 -0.7510 0.3433 0.9998 0.3813 -0.7235 -0.9056 0.0672 0.9543 0.6244 -0.5018 -0.9880 -0.2143 0.8328 0.8178 -0.2401

plot(A_real,A_imag)

hold on

P_real=real(RP)

P_real = 1×301

-3.8675 2.9171 -5.5663 -1.7785 -4.8323 1.6248 3.3844 1.8513 -1.5249 -2.4793 -0.2238 0.0130 4.5774 -2.5654 4.4553 5.4299 0.2248 2.6124 3.0542 -2.5154 -3.9619 -3.8939 -3.5367 -5.6547 -1.6590 -0.4626 5.1432 5.1124 -0.0507 1.6366

P_imag=imag(RP)

P_imag = 1×301

1.1434 -3.3660 1.9724 4.4791 -0.1042 4.6762 -3.3649 5.2569 -5.1451 3.4664 -5.4213 5.5288 -0.2998 4.8545 -1.8001 0.7494 -4.6054 -3.2759 -2.6469 -5.3785 1.4949 1.1027 -2.2532 -0.4928 4.4348 3.9738 2.5499 -1.2209 5.7901 -4.5064

plot(P_real,P_imag)

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Answer 1

Les Beckham 2023-11-2

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https://ww2.mathworks.cn/matlabcentral/answers/2041986-why-does-the-figure-doesnt-show-the-two-vectors#answer_1345441

编辑：Les Beckham 2023-11-2

在 MATLAB Online 中打开

It looks like it is working to me (see below). What are you expecting and how is that different from the results you are seeing?

%Links length

L1=5; L2=1; L3=5; L4=7; AP=5;

% ternary link angle (degree)

delta=50;

th2= 0:1.2:360;

range_th2=300;

RP=zeros(1,range_th2);

RA=zeros(1,range_th2);

i=1;

while i<=301

% the loop variables

R1=L1;

R2=L2*(cos(th2(i))+sin(th2(i))*1i);

Z=R1-R2;

Zconj=conj(Z);

% Quadratic equation parameters

a=L4.*Zconj;

b=Z.*Zconj+L4.^2-L3.^2;

c=L4*Z;

T=roots([a b c]);

T_pos=T(2);

%T_pos=(-b+sqrt(b.^2-4.*c.*a))/(2.*a);

S=(L4*T_pos+Z)/L4;

% solution

th3(i)=rad2deg(angle(T_pos));

th4(i)=rad2deg(angle(S));

R3=L3*(cos(th3(i))+sin(th3(i))*1i);

R4=L4*(cos(th4(i))+sin(th4(i))*1i);

thAP=th3(i)-delta;

RAP=AP*(cos(thAP)+sin(thAP)*1i);

%position of A and P

RA(i)=R2;

RP(i)=R2+RAP;

i=i+1;

end

A_real=real(RA);

A_imag=imag(RA);

plot(A_real,A_imag);

hold on

P_real=real(RP);

P_imag=imag(RP);

plot(P_real,P_imag)

axis equal

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shamma aljaberi 2023-11-2

Im expecting a circular shape for RA and more like an Ellipse shape for RP

Les Beckham 2023-11-2

I edited my answer to add "axis equal" so the x and y scales are equal. They are both pretty circular in shape. Have you double checked the equations?

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Answer 2

dpb 2023-11-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2041986-why-does-the-figure-doesnt-show-the-two-vectors#answer_1345446

编辑：dpb 2023-11-2

在 MATLAB Online 中打开

%Links length

L1=5; L2=1; L3=5; L4=7; AP=5;

% ternary link angle (degree)

delta=50;

th2= 0:1.2:360;

range_th2=300;

RP=zeros(1,range_th2);

RA=zeros(1,range_th2);

i=1;

while i<=301

% the loop variables

R1=L1;

R2=L2*(cos(th2(i))+sin(th2(i))*1i);

Z=R1-R2;

Zconj=conj(Z);

% Quadratic equation parameters

a=L4.*Zconj;

b=Z.*Zconj+L4.^2-L3.^2;

c=L4*Z;

T=roots([a b c]);

T_pos=T(2);

%T_pos=(-b+sqrt(b.^2-4.*c.*a))/(2.*a);

S=(L4*T_pos+Z)/L4;

% solution

th3(i)=rad2deg(angle(T_pos));

th4(i)=rad2deg(angle(S));

R3=L3*(cos(th3(i))+sin(th3(i))*1i);

R4=L4*(cos(th4(i))+sin(th4(i))*1i);

thAP=th3(i)-delta;

RAP=AP*(cos(thAP)+sin(thAP)*1i);

%position of A and P

RA(i)=R2;

RP(i)=R2+RAP;

i=i+1;

end

A_real=real(RA);

A_imag=imag(RA);

plot(A_real,A_imag);

hold on

P_real=real(RP);

P_imag=imag(RP);

plot(P_real,P_imag);

axis equal

legend('A','P')

figure, subplot(2,1,1) % look versus order instead

plot(A_real), hold on, plot(A_imag)

xlim([1 100])

legend('A_R','A_I')

subplot(2,1,2) % look versus order instead

plot(P_real), hold on, plot(P_imag)

legend('P_R','P_I')

xlim([1 100])

What we observe is that the "A" traces are pretty clean sinusoids with just a phase difference; hence the real vs imaginary parts follow a decent trace as shown on the first.

On the other hand, the "P" traces are much more random appearing; movements aren't smooth from one observation to the next; hence the two plotted against each other reflect that...

What you were expecting is unknown to us...we don't know the problem statement.

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Voss 2023-11-2

在 MATLAB Online 中打开

Fixing the degree/radian units issue, based on @dpb's observation, produces a more interesting plot. Maybe that's closer to what's intended, @shamma aljaberi?

%Links length

L1=5; L2=1; L3=5; L4=7; AP=5;

% ternary link angle (degree)

delta=50;

th2= 0:1.2:360;

range_th2=300;

RP=zeros(1,range_th2);

RA=zeros(1,range_th2);

i=1;

while i<=301

% the loop variables

R1=L1;

R2=L2*(cos(th2(i))+sin(th2(i))*1i);

Z=R1-R2;

Zconj=conj(Z);

% Quadratic equation parameters

a=L4.*Zconj;

b=Z.*Zconj+L4.^2-L3.^2;

c=L4*Z;

T=roots([a b c]);

T_pos=T(2);

%T_pos=(-b+sqrt(b.^2-4.*c.*a))/(2.*a);

S=(L4*T_pos+Z)/L4;

% solution

th3(i)=rad2deg(angle(T_pos));

th4(i)=rad2deg(angle(S));

R3=L3*(cosd(th3(i))+sind(th3(i))*1i);

R4=L4*(cosd(th4(i))+sind(th4(i))*1i);

thAP=th3(i)-delta;

RAP=AP*(cosd(thAP)+sind(thAP)*1i);

%position of A and P

RA(i)=R2;

RP(i)=R2+RAP;

i=i+1;

end

A_real=real(RA);

A_imag=imag(RA);

plot(A_real,A_imag)

hold on

P_real=real(RP);

P_imag=imag(RP);

plot(P_real,P_imag)

axis equal

legend('A','P')

figure, subplot(2,1,1) % look versus order instead

plot(A_real), hold on, plot(A_imag)

xlim([1 100])

legend('A_R','A_I')

subplot(2,1,2) % look versus order instead

plot(P_real), hold on, plot(P_imag)

legend('P_R','P_I')

xlim([1 100])

dpb 2023-11-2

@Voss -- thanks, I got interrupted before I got a chance to look more to see if that was the only place -- maybe the alternative fix would be to simply remove the calls to rad2deg() unless the angles are being displayed in those units elsewhere.

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why does the figure doesnt show the two vectors?

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why does the figure doesnt show the two vectors?

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