a loop problem in matlab

My code is:

for p=1:0.01:2;
    plot3(p,p.^2,p.^3);
end

I want to use a loop of p to create a three dimentional figure. while no error occurs, the figure is strange. I simplify my code into the above code. Any help is very appreciated! Thanks.

[Adam Danz]

A solution was provided below but it does not explain why your code doesn't work and that's the important part.

There are two problems.

1) When you're plotting in a loop (which often can be avoided), you need to 'hold' the axes to prevent the plot from being over-written on each iteration. That would look something like this:

figure
ah = axes; 
hold(ah, 'on')
for
    plot(ah, x, y)
end

2) On each iteration of your for-loop, you're plotting a single point and since you didn't specify a marker type, plot3 is trying to draw a line. You can't draw a line with a single point which is why your plot ended up completely empty. One solution would have been to specify a marker type :

plplot3(p, p.^2, p.^3, 'bo')

But the best solution is to avoid the loop altogether as is demonstrated in the answer below.

[James_111]

Thank you so much for your detailed explaination. Maybe I should post my competed code again. My code has a fzero function makes it more complicated.

Answer 1

[madhan ravi]

Without loop:

p=1:0.01:2;
plot3(p,p.^2,p.^3);  % no loops needed
grid on

With loop:

p=1:0.01:2;
h = animatedline; 
grid on
view(3); % lookup doc
for i=1:numel(p)
addpoints(h,p(i),p(i)^2,p(i)^3);
drawnow
end

[James_111]

Thanks. Your appraoch solves the issue in my simplified code. Can you help me take a look at my another code?

https://www.mathworks.com/matlabcentral/answers/439076-fzero-cannot-continue-because-user-supplied-function_handle-a-and-b-must-be-floating-point-scalars?s_tid=prof_contriblnk

[madhan ravi]

Anytime :) , sure let me try and sorry I missed your reply there , let me get some sleep and then get back to you there.