How to create contour plot to show height?

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Muhammad Qaisar Fahim 2022-3-18

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https://ww2.mathworks.cn/matlabcentral/answers/1674504-how-to-create-contour-plot-to-show-height

评论： DGM 2022-3-21

I want to create a countour plot such that my x axis and y axis are the coordinates of the plane and my z axis is height. I want to creat a 2b plot (contour) such that my height is differentiated with color. My z value has no relation with xy value other that the first value of z is corresponding to the cobination of first two values of x and y.

For example my x, y and z vectors are:

AAA=1:1:1000;

BBB=1:1:1000;

CCC=2:2:2000;

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Muhammad Qaisar Fahim 2022-3-18

The correlation is that for each pair of x and y there is a corresponding value of z but the limitataion is that we only have one to one correspondance i.e., 1st value of x and first value of y corresponds to first value of z but first value of x and 2nd value of y corresponds to nothing.

DGM 2022-3-18

Okay, yeah. That's just scattered data. Walter's suggestion looks pretty good.

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Answer 1

DGM 2022-3-19

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https://ww2.mathworks.cn/matlabcentral/answers/1674504-how-to-create-contour-plot-to-show-height#answer_921464

在 MATLAB Online 中打开

scattered.mat

You can always try just using griddata()

S = load('scattered.mat'); % load scattered data

n = 100;

x = linspace(min(S.x),max(S.x),n);

y = linspace(min(S.y),max(S.y),n);

[xg yg] = meshgrid(x,y); % create new grid

zg = griddata(S.x,S.y,S.z,xg,yg); % interpolate scattered data to grid

contour(xg,yg,zg) % now you can use contour(), contourf(), surf(), etc

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DGM 2022-3-21

编辑：DGM 2022-3-21

在 MATLAB Online 中打开

So you basically want variable-color lines. There are two basic ways to do that.

First, you could use a very dense scatter plot to create pseudolines. This is the simple way, and the data doesn't need to be ordered.

cmap = parula(64);

N = 1000; % how many points to plot?

x = linspace(0,10,N); % a straight line

y = linspace(0,10,N);

z = sin(linspace(-pi/2,7*pi/2,N)); % sinusoidally-varying z-height

h = scatter(x,y,10,z,'filled');

colormap(cmap);

colorbar

Alternatively, you can use a surf() plot. This will actually create lines, so the data needs to be ordered.

cmap = parula(64);

N = 100; % how many points to plot?

x = linspace(0,10,N); % a straight line

y = linspace(0,10,N);

z = sin(linspace(-pi/2,7*pi/2,N)); % sinusoidally-varying z-height

h = surf([x(:) x(:)],[y(:) y(:)],[z(:) z(:)]);

set(h,'facecolor','none','edgecolor','interp');

set(h,'linewidth',3); % make it fat so it's easier to demonstrate

view(2); % only show 2-D view

colormap(cmap);

colorbar

That said, I don't know how exactly this data is arranged -- how dense it is, etc. It may become complicated if the points are relatively sparse and unordered.