MATLAB: Error using contour function

contourplotting

When attempting to produce a contour plot of an equation i have named as Z. I am presented with the error shown below.

Can anyone help?

Best Answer

You need to use ‘X’ and ‘Y’ in ‘Z’.

Try this:

x = linspace(-1, 1, 100);
y = linspace(-1, 1, 100);
[X,Y] = meshgrid(x, y);
a = x + 0.5;
b = y - 0.5;
Z = @(x,y) 1./sqrt(a.^2 + y.^2) - 2./sqrt(b.^2 + x.^2);
figure(1)
contour(X, Y, Z(X,Y))

Related Solutions

MATLAB: How to plot a mesh

Use meshgrid to create the ‘X’ and ‘Y’ meshes, then calculate ‘Z’ from them:

x = linspace(-3, 3, 50);
y = linspace(-1.5, 1.5, 30);
[X,Y] = meshgrid(x, y);
Z = sin(X) .* exp(Y);
figure(1)
mesh(X, Y, Z)
grid on

Note the use of element-wise multiplication (.*) in ‘Z’.

MATLAB: Contour plot for given x,y,z


[num,txt,raw] = xlsread('Book1.xlsx') ; 
x = num(:,1) ; 
y = num(:,2) ; 
z = num(:,3) ; 
figure(1)
scatter(x,y,20,z,'filled') ; colorbar
%% Method 1 / Griddata
nx = 500 ; ny = 500 ;
[X,Y] = meshgrid(linspace(min(x),max(x),nx),linspace(min(y),max(y),ny)) ;
Z =griddata(x,y,z,X,Y) ;
figure(2)
contour(X,Y,Z) ;
figure(3)
pcolor(X,Y,Z)
shading interp 
%% Method 2 simple reshaping 
x = unique(x) ; nx = length(x) ;
y = unique(y) ; ny = length(y) ;
Z = reshape(z,ny,nx) ;
figure(4)
contour(x,y,Z)

Best Answer

Related Solutions

MATLAB: How to plot a mesh

MATLAB: Contour plot for given x,y,z

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