MATLAB: Gradient of a 2D plot

2d plotcontourgradientquivervector field

I have a 2D plot of potential (V) (circular contour plot). I have to find the electric field (E) by taking the gradient. How is it possible to see the gradient of V. [U,W]=gradient(V) returns the gradient in X and Y direction and quiver(X,Y,U,W) helps to visualize the vector field. How is it possible to view effective gradient. Contour (X,Y,U) will only help me to see gradient in x direction. How can I see the effect of gradient which is a vector sum of both gradient in X and Y.?

Best Answer

See the gradient documentation section on Contour Plot of Vector Field . It demonstrates exactly what you are describing.

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MATLAB: Error using optimoptions (Reference to non-existent field ‘TolFunValue’)

For optimoptoptions the correct option is FunctionTolerance. The usage of TolFunValue is the equivalent option when you use optimset instead. See here for more details.

MATLAB: Quiver lines on contour not showing

There seems to be a problem with the way you’re calculating the gradient. Making these changes will allow you to see the vectors and the contour plot (that I temporarily turned into contourf to make it visible). I will defer to you to determine what you need to do to fix it with the vector scaling turned back on:

   [px,py]=gradient(Sum, 1E+4, 1E+4);         % Set Derivative Intervals
   figure(1)
   contourf(x,y,Sum,n)
   hold on
   quiver(x,y,px,py,0)                        % Turn Off Scaling
   hold off

Best Answer

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MATLAB: Error using optimoptions (Reference to non-existent field ‘TolFunValue’)

MATLAB: Quiver lines on contour not showing

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