how to plot Contour Plot?

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Radhika Kulkarni 2019-12-15

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评论： Star Strider 2019-12-15

I have 3 variables data in xls file. I want to plot contour plot of one variable against other 2 variables on x and y axis. How do I do this?

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Star Strider 2019-12-15

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I assume your variables are vectors. If they are gridded, it is only necessary to use the reshape function to form them into matrices.

If they are not gridded, something like this will work:

x = rand(20, 1);
y = rand(20, 1);
z = rand(20, 1);
xv = linspace(min(x), max(x), 50);
yv = linspace(min(y), max(y), 50);
[X,Y] = ndgrid(xv, yv);
Z = griddata(x, y, z, X, Y);
figure
contourf(X, Y, Z)

Experiment to get the result you want.

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Radhika Kulkarni 2019-12-15

My contour lines value is showing as 80.34678, how do I round it of to 80 and so on?

Star Strider 2019-12-15

在 MATLAB Online 中打开

If you know the values you want for the contours, the easiest way is to specify them in a vector as the fourth argument to contourf:

x = rand(20, 1);
y = rand(20, 1);
z = rand(20, 1)*100;
xv = linspace(min(x), max(x), 50);
yv = linspace(min(y), max(y), 50);
[X,Y] = ndgrid(xv, yv);
Z = griddata(x, y, z, X, Y);
colorcol = linspace(0.1, 0.9, 10);                      % Define Number Of Intensities (Here 10)
cmap = zeros(numel(colorcol), 3);                       % Define ‘colormap’ Here
cmap(:,2) = colorcol(:);                                % Choose Green ([R G B])
figure
contourf(X, Y, Z, [20 40 60 80], 'ShowText','on')
colormap(cmap)