Plotting Multivariable x, y, and z for a data set

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SugerCodeCude 2020-10-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/605381-plotting-multivariable-x-y-and-z-for-a-data-set

评论： Star Strider 2020-10-6

I have made a 3d multivatiable gird that is, x, y, and z

grid_x = 1:1:10;
grid_y = 1:1:10;
grid_z = 1:1:10;

then in a 3 loop (3d multivariable) I calculate values for a give equation and save is it in a variable called values(:,:). the multivariable values has points between 1:10 random numbers

Now I have used

[X,Y] = meshgrid(grid_x,grid_y);
Z = griddata(grid_x,grid_y,grid_z,X,Y);

however Z is not where the values are, when I call

surf(X,Y,Z)

I get a empty plot in 3d, here is where I am not understand how to call in the data points which is called values, even when I did

surf(X,Y,Z,values(:,:))

I get a empty plot in 3d.

Please tell me to clarify if needed.

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Answer 1

Star Strider 2020-10-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/605381-plotting-multivariable-x-y-and-z-for-a-data-set#answer_505516

在 MATLAB Online 中打开

The problem is with your choice of coordinates.

When I ran your code, it threw:

Warning: The underlying triangulation is empty - the points may be collinear. 
> In griddata>useScatteredInterp (line 183)

and ‘Z’ was empty.

Creating random values instead resulted in the sort of result you want:

grid_x = rand(1,50);
grid_y = rand(1,50);
grid_z = randn(size(grid_x));
[X,Y] = meshgrid(0:0.01:1, 0:0.01:1);
Z = griddata(grid_x,grid_y,grid_z,X,Y);
figure
surf(X,Y,Z)
grid on

.

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SugerCodeCude 2020-10-5

在 MATLAB Online 中打开

3 Dimensions, x- and y- axis having all the same range between 1-10, and z has 10 dimension, and in dimension 1 for z it has a range between 1-10.

grid_x = 1:1:10;
grid_y = 1:1:10;
% here will be the grid for the 10 dimensions
grid_z = 1:1:10;
% make the meshgrid
[X,Y] = meshgrid(grid_x, grid_y);
% Here in the loop; is where you are saying I am not using the Z variable 
% to put my values in,
% rather I'm putting it into another variable called values
for z = grid_z
    for x = grid_x
        for y = grid_y
            
            % Here is where I am not using Z to store the value I get
            % please tell me do you see where I am making the mistake
            % I think this is used here.
            % I can't understand where this comes into play?
            % pseudo code
            Z = griddata(grid_x,grid_y,grid_z,rand(),X,Y);
        end
    end
end
figure
surf(X,Y,Z)
grid on

You are telling me to use Z, I believe I am having a problem in how to implemented it in? I do understand what you are telling me.

For Z in dimension 1 it will go through the loop and get the values, then next dimension 2 it will have all the values for it... so on. I guess that is what I need help on.

and for simplicity sake I am making the grid 10x10x10 (x, y, z);

Please tell me if I'm in the ballpark

SugerCodeCude 2020-10-5

在 MATLAB Online 中打开

It is starting to make sence, here is why I am using the loop and tell me how and where to implement the Z

grid_x = 1:1:10;
grid_y = 1:1:10;
grid_z = 1:1:10;
% make the meshgrid
[X,Y] = meshgrid(grid_x, grid_y);
% Here in the loop; Why the loop? 
for z = grid_z
    for x = grid_x
        for y = grid_y
            
            % the loop variable z, x, and y are passed into a function to give values 
            % for each of the grid points
            % [values_1]=function(z,x,y)
            
            % a for loop then I compares the values_1 to another values_2 
            % (values_2 are data points I have)
            % bestFit(i)= min(abs(values_1-values_2)) by using a for loop between a small range
            % i++;
            % end the for loop
            
            %then I do the sqrt and the mean, how can I use the Z to put in the values I get 
            % weather I use griddata or griddedinterpolant I think I need help here.
            Z = griddata(grid_x,grid_y,sqrt(mean(bestFit(:))),X,Y);
            
        end
    end
end

Yes, I do agree no need to use the loop, as I am very fond of Matlabs power. but this is why I use the loop, and you are right I can use the sqrt and mean in the Z, and not use the loop as Matlab will take care of it.

however, I get it Z is 10 by 10 ok, for each sqrt and mean of the bestFit values I like it to go into it matrix place (x, and y position)

By the way THANK YOU!! SO MUCH for bearing with me

SugerCodeCude 2020-10-6

Thank you so mch, this back and forth help me understand the issues I was having. Thank you again!

Star Strider 2020-10-6

As always, my pleasure!

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Plotting Multivariable x, y, and z for a data set

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