3d plot with x value being constant

im trying to plot a point on a 3d plot but i keep coming up with the error

Error using plot3

Vectors must be the same length.

Error in threed_suspension (line 50)

plot3(Lowerx,Lowery,Lowerz,'b')

I dont know how to keep p5x constant while p5y and p5z a changing variable.

p5y(i)= RL*cosd(LowerTheta(i));

p5z(i)=RL*sind(LowerTheta(i)); %parallel

z=size(LowerTheta);

p5x= p1x*z;

Lowerx=[p1x,p5x];

Lowery=[p1y,p5y(i)];

Lowerz=[p1y,p5z(i)];

plot3(Lowerx,Lowery,Lowerz,'b')

plot3(p5x,p5y,p5z,'*r')

Answer 1

[Askic V]

p5x= p1x*ones(z);

[Darren Marcelino]

im still getting the same error.

here is my entire code:

%% 3d plot

clc

close all

clear all

RL=12;

LowerTheta= 22:-2:-14;

for i=1:length(LowerTheta)

%p1 Lower back mounting point

p1x=0;

p1y=0;

p1z=0;

plot3(p1x,p1y,p1z,'*r')

grid on

hold on

xlabel('x')

ylabel('y')

set(gca, 'YDir','reverse')

zlabel('z')

%p2 upper back mounting point

p2x= p1x;

p2y= p1y;

p2z= 5;%vertical distance in inches

plot3(p2x,p2y,p2z,'*r')

%p3 lower front mounting point

p3x=10;%horizontal distance between lower mounts

p3y=p1y;

p3z= p1z;

plot3(p3x,p3y,p3z,'*r')

%p4 upper front mounting point

p4x=p3x;%dist between upper mounts

p4y=p2y;%

p4z=p2z;%height

plot3(p4x,p4y,p4z,'*r')

%p5 lower arm member

p5y(i)= RL*cosd(LowerTheta(i));

p5z(i)=RL*sind(LowerTheta(i)); %parallel

z=size(LowerTheta);

p5x= p1x*ones(z);

Lowerx=[p1x,p5x];

Lowery=[p1y,p5y(i)];

Lowerz=[p1y,p5z(i)];

plot3(Lowerx,Lowery,Lowerz,'b')

plot3(p5x,p5y,p5z,'*r')

%p6 upper arm member

p6x= p2x;

p6y(i)= RL*cosd(LowerTheta(i));

p6z(i)=RL*sind(LowerTheta(i)); %parallel

plot3(p5x,p5y,p5z,'*r')

end

[Darren Marcelino]

so ive got it to plot the length i want, but now im having trouble making go through each itteration.

%% 3d plot

clc

close all

clear all

RL=12;

LowerTheta= 22:-2:-14;

for i=1:length(LowerTheta)

clf

%p1 Lower back mounting point

p1x=0;

p1y=0;

p1z=0;

plot3(p1x,p1y,p1z,'*r')

grid on

hold on

xlabel('x')

ylabel('y')

set(gca, 'YDir','reverse')

zlabel('z')

%p2 upper back mounting point

p2x= p1x;

p2y= p1y;

p2z= 5;%vertical distance in inches

plot3(p2x,p2y,p2z,'*r')

%p3 lower front mounting point

p3x=10;%horizontal distance between lower mounts

p3y=p1y;

p3z= p1z;

plot3(p3x,p3y,p3z,'*r')

%p4 upper front mounting point

p4x=p3x;%dist between upper mounts

p4y=p2y;%

p4z=p2z;%height

plot3(p4x,p4y,p4z,'*r')

%p5 lower arm member

p5y(i)= RL*cosd(LowerTheta(i));

p5z(i)=RL*sind(LowerTheta(i)); %parallel

z=size(LowerTheta);

p5x= repmat(p1x,1,length(p5y));

Lowerx=[p1x,p5x(i)];

Lowery=[p1y,p5y(i)];

Lowerz=[p1y,p5z(i)];

plot3(Lowerx,Lowery,Lowerz,'b')

plot3(p5x,p5y,p5z,'*r')

%p6 upper arm member

p6x= p2x;

p6y(i)= RL*cosd(LowerTheta(i));

p6z(i)=RL*sind(LowerTheta(i)); %parallel

plot3(p5x,p5y,p5z,'*r')

end

[Askic V]

Did you try this?

%p5 lower arm member
    p5y(i)= RL*cosd(LowerTheta(i));
    p5z(i)=RL*sind(LowerTheta(i)); %parallel 
    p5x(i) = p1x;
    Lowerx=[p1x,p5x(i)];
    Lowery=[p1y,p5y(i)];
    Lowerz=[p1y,p5z(i)];

I'm not really sure what you want to do, but if you need p5x to be constant, just assign it value just like on y and z component.

[Darren Marcelino]

I ended up figuring that spherical coordinates are easier to manipulate and keep stuff constant. i rewrote my code using spherical coordinates. i found it easier. i had to do extra trig to figure out angles but i found that if you are trying to keep a length constant, one end of it is pinned. (360 freedom of movement) , and the other end is moving in the 3d space, spehrical coordinates are best to use.

https://www.mathworks.com/help/phased/ug/spherical-coordinates.html