Fixing a choppy plot

Hi, I have the following code in Matlab and the red helix is coming out choppy. I am new to this and trying to make it look pretty! I wanted to have the red and blue plots display together, and then place a point on one of them; placing a green point on an intersection would be cool. (I can figure that out math wise, but I don't know how to make the green point "pop out") Thanks for any help!

t = 0:pi/20:10*pi;
xt = sin(t);
yt = cos(t);
plot3(xt,yt,t,'-o','Color','b','MarkerSize',10)



hold on

t5 = 5;
xt5 = sin(5);
yt5 = cos(5);
plot3(t5,xt5,yt5,'MarkerSize',200,'Color','g')

xt = sin(5*t);
yt = cos(5*t);
plot3(xt,yt,t,'-','Color','r','MarkerSize',10)


hold off
axis equal
xlim([-1, 1]); 
ylim([-1, 1]); 
zlim([0, 5]);

Answer 1

[Image Analyst]

You don't have many points in t. Try using linspace and specify a larger number.

t = linspace(0, 10*pi, 2000);
xt = sin(t);
yt = cos(t);
plot3(xt,yt,t,'-o','Color','b','MarkerSize',10)
hold on

t5 = 5;
xt5 = sin(5);
yt5 = cos(5);
plot3(t5,xt5,yt5,'MarkerSize',200,'Color','g')

xt = sin(5*t);
yt = cos(5*t);
plot3(xt,yt,t,'-','Color','r','MarkerSize',10)

hold off
axis equal
xlim([-1, 1]); 
ylim([-1, 1]); 
zlim([0, 5]);

[Joshua Leiter]

Awesome! Thanks this solved my problem! I appreciate the help!

[Image Analyst]

If youi want the green spot to be on top, you can plot it last, after everything else has plotted. Thanks for Accepting. 🙂

Answer 2

[William Rose]

@Joshua Leiter,

The plot order on the line to plot the green marker was wrong. Fixed. Fill in the marker with MarkerFaceColor, and black outline, to make it pop out. Extend z (time) axis. Add grid to help viewer appreciate the 3D perspective. See attached.

t = 0:pi/20:10*pi;
xt = sin(t);
yt = cos(t);
plot3(xt,yt,t,'-o','Color','b','MarkerSize',10)
hold on
t5 = 5;
xt5 = sin(5);
yt5 = cos(5);
plot3(xt5,yt5,t5,'ko','MarkerSize',15,'MarkerFaceColor','g')
xt = sin(5*t);
yt = cos(5*t);
plot3(xt,yt,t,'-','Color','r','MarkerSize',10)
hold off, grid on
axis equal
xlim([-1, 1]); 
ylim([-1, 1]); 
zlim([0, 6]);

Good luck!

[Joshua Leiter]

Oooo! This is great! Thanks this also really helps! I appreciate all the syntaxical things I missed! No wonder it wasn't working.... The MarkerFaceColor comment is really helpful too

[William Rose]

@Joshua Leiter, you're welcome.