Hi,
It is my understanding that you are having problem on how to plot tubes where the inputs for the plot should be controlled by you. For tube plots you can use the function which is available on file exchange where you can control the inputs and the get the desired tube as the output.
The link for the function available on file exchange is given below.
For this particular function you can try the following example for more clarity
t=linspace(0,2*pi,50);
tubeplot([cos(t);sin(t);0.2*(t-pi).^2],0.1);
There is another method for plotting tubes available on MATLAB, ‘streamtube’. Even here the input can be varied by the user and the plot created is through the vector volume data provided.
The documentation link for ‘streamtube’ is given below
