X,Y data of irregular grid, scatter plot with Z data

Question

Willemijn Wolf 2020-1-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/501504-x-y-data-of-irregular-grid-scatter-plot-with-z-data

评论： Star Strider 2020-1-23

采纳的回答： Star Strider

Demonstration_data_xyz.txt

在 MATLAB Online 中打开

Dear all,

I know that there is the possibility to create a scatter plot using X and Y and reshaping the Z data, such that:

Z = reshape(Z, [X Y]);
figure()
imagesc (Z)

This creates a square 2D plot like depicted above.

However, I have a different problem now in which X,Y,Z data is already given to me (see text file attached).

The X,Y data include the coordinates of the center of a square. Z is the data that I would like to visualize by a scatter plot just like the example above. Now my 2D 'grid' on which I like to depect my Z data on looks like this:

So I have 2 questions

Is there an easy way to create a nice rectangular grid out of these center points (still working with Matlab 2016, so no rectangle function yet...)? Or from the coordinates that I have on each node of one rectangular (see txt file attached).
How to include my Z data such that I can create a scatter plot?

-> I know it is not a highly complicated problem, but I'm afraid that I might miss out some easy Matlab functions that are very convenient to use in my case.

Many thanks for any tips

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Answer 1

Star Strider 2020-1-22

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/501504-x-y-data-of-irregular-grid-scatter-plot-with-z-data#answer_411493

在 MATLAB Online 中打开

It is not obvious to me what you want.

You already appear to have tried reshape, although I have no idea what the arguments to it were, since we do not have that part of your code.

Try this:

filename = 'Demonstration_data_xyz.txt';
fidi = fopen(filename,'rt');
Dc = textscan(fidi, '%f%f%f%f%f%f%f%f%f%f%f%f', 'HeaderLines',1', 'CollectOutput',1, 'EndOfLine','\r\n', 'Delimiter',' ', 'MultipleDelimsAsOne',1);
Dd = [Dc{:}];
XYZ = Dd(:,10:12);
didx = diff([1; find(diff([0; XYZ(:,1)]) < 0));
Xmtx = reshape(XYZ(:,1), mean(didx), []);
Ymtx = reshape(XYZ(:,2), mean(didx), []);
Zmtx = reshape(XYZ(:,3), mean(didx), []);
figure
surf(Xmtx, Ymtx, Zmtx)