Plot Surface when Z is not a function of X and Y

Hi everyone.

I am trying to plot my data in 3D surface. However, it currently does not work since my X,Y, and Z are independent. Z is not F(X,Y). I also try to use meshgrid but still does not work. The reason that I want to plot surface because my scatter plot points are trade-off. Thus, if i can show it in surface, it will be easier to interpolate my trade-off. Do I have any other ways to use surf function?

Thank you very much.

Answer 1

[Image Analyst]

What relationship is there between z and x and y? What is z? Is it a 2D matrix? Is it a vector? Is it a volumetric array, like a CT or MRI image?

[OoM]

There is no relationship with each others. One point represents X as time, Y as direct cost, and Z as indirect cost. I could plot 3D scatter. My 1000 points results look like they can plot surface connecting points.

[Image Analyst]

Why not just do

surf(Z);

Attach any visualizations you can to help us understand what you want or what you are getting.

[OoM]

Here is the results in 3D Scatter plot. Each color represents each simualtion run. I would like to make surface plot of each set of color.

[Meva]

I have a question related to this. My Z function depends on X, Y but not directly. So I plot my Z function using surf(Z). The problem is x, and y axes are wrong and I cannot change them. They supposed to be between 0 and 1 but they are between 0 and 100

[Steven Lord]

From the documentation for the surf function:

 surf(Z) creates a three-dimensional shaded surface from the z
 components in matrix Z, using x = 1:n and y = 1:m, where
 [m,n] = size(Z).

You want to use this syntax for surf:

 surf(X,Y,Z) uses Z for the color data and surface height.
 X and Y are vectors or matrices defining the x and y components
 of a surface.

X, Y, and Z don't need to be related, but if you specify all three they must be compatibly sized as described in the documentation. For example, this is a valid call to surf where Z is completely random and so is not a function of either X or Y.

>> x = 1:10:100;
>> y = x.^2;
>> z = randn(10);
>> surf(x, y, z)

[Meva]

When I tried yours, yes it works. When I tried mine, it does not.

Error is the following :

Data dimensions must agree. surf(t,x,u1array)

My u1array : 201*101 sized array.

t = 0:0.01:2;

x = 0: 0.01:1;

If I type,

t = 0:dt:2;
x=0:dx:1;
surf(t,x,u1array)

it gives above error.

If I type,

surf(u1array)

it gives a surface plot but x and y axes are not what I want . The x and y axes should be in t and x range.

[Steven Lord]

Another quote from the documentation page:

 If X and Y are vectors, length(X) = n and length(Y) = m,
 where [m,n] = size(Z).

Since u1array is of size [201, 101] we have m = 201 and n = 101. The length of your X vector must be 101 and the length of your Y vector must be 201. As written, they aren't. To correct this, inside your surf call either swap the positions of t and x (use x as the first input and t the second) or transpose u1array.

[Meva]

The weird thing is this point actually. I tried this before posting my previous comment. However,

surf(x,t,u1array)

does not work as well.

[Meva]

I just want to know whether Matlab can do this or not,

[Torsten]

t=0:0.01:2;
x=0:0.01:1;
surf(x,t,u1array);

does not work for u1array being 201x101 ?

That's surprising.

Best wishes

Torsten.

[Meva]

Thanks Torsten. My t and x arrays are very above my code and somehow it did not put the right axes limits. Now it is working. Thanks so much.