I found the following post helpful http://www.mapleprimes.com/posts/41250-Using-DEplot3d#comment76752

hirnyk 469 has a good hint, but I was looking for a way to give a list of initial conditions, so that I can adjust to view the plot.

Based on this comment, I change my initial conditions as follows:

Then follow the syntax for DEplot3d:

Thank you.
It is a little strange, but it works!!!

I used the following pointplot() command (listed below), and it still does not achieve the graph I'd like. I like the data points are connected by a line, AND the data points must be shown (or marked with a circle, or a diamond). I do not like the graph will only scatter points.
=== code
stressStrainPlot := pointplot(stressStrainData, connect = true, symbol = circle, labels = [engrStrain, engrStress], color = red)

Hi Doug, Scott, and Acer:
Thank you for all your answers; I've learned a lot from reading all the answers.
~ -- to work with elmentwise work fine
Array -- work fine.
Side notes: I had turned to MATLAB to get the answers quickly. I find MATLAB is a little more "intuitive" when dealing with array, list, vector; by "intuitive" I mean that users will not need to 'think' about "element operations". But I like the plotting features of Maple; I now come back to work on this problem using Maple.
Thank you for your help.
--mdc

Did you suggest that instead of

1/4 * (sin^2(t) - cos^2(t))

I should use:

1/4* ( (sin(t))^2 - (cos(t))^2)

?

The error is rid of. So, it is great. Thanks

WRT: whether or not I get the answer I expect... I did not get the result I expect though. I also use Stoke Theorem with surface integral, and the two integrals are not equal. It is other problem. Thanks.

With(VectorCalculus): was mispelled!!!

It is one very frustrating problem with Maple, its errors detection and error messages are very vague.

Thank you all for your help.

With(VectorCalculus): was mispelled!!!

It is one very frustrating problem with Maple, its errors detection and error messages are very vague.

Thank you all for your help.

Hi Patrick,

Thank you for your time. I will look into it further.

** I alwasy have restart at the top of my file

** I use Maple for Students. I tried with With (Student[VectorCalculus]): and have the same problem.

Thanks

HI PatrickT:

I'm sorry for not being clear; but I do have with(VectorCalculus): in my .mw file; I neglected to mention.

Even with with(VectorCalculus): I still have the error

> r1 := diff(R(r, t), r);

Error, non-algebraic expressions cannot be differentiated

>

Any ideas?

Hi Alex,
I typed in what you suggested, I got the following error with the diff:
> r1 := diff(R(r, t), r);
Error, non-algebraic expressions cannot be differentiated
> r2 := diff(R(r, t), t);
Error, non-algebraic expressions cannot be differentiated
Any suggestion?
Thanks

Thanks, Pagan.
Your comment gives me some insights to what I did wrong.
Z = xy is one of the hyperbolic paraboloids. To parameterize it, the equation is:
x=r*cos(t)
y=r*sin(t)
z=r^2*cos(t)*sin(t)

Reading your explanations, I think the way I parameterize the surface z=xy is erroneous. i.e. x=cos(t) y=sin(t) is not a correct way to parameterize z, in this case.
Ideas?

In the past I was able to use plot3d or plot to plot a parametric surface.
For example, if given a cone of z = sqrt(x^2 + y^2), I would parameterize it as:
x = r*cos(t), y=r*sin(t), r and use plot3d to plot the surface of the cone.
c := plot3d([r*cos(t), r*sin(t), r], t = 0 .. 2*Pi, r = 0 .. 2, axes = boxed, labels = [x, y, z], color = "Crimson")
It works fine.
The above error has something with the syntax, not the intention of my usage, I think.
Idea?

I find the answer to my own question.

I retyped carefully and do get the same value. (Sigh!!!). Thank you.