Gradient of a 2D plot

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.?

[Ameer Hamza]

What is wrong with quiver. It generates arrows in the gradient direction.

[Prince Alex]

I am looking for contourf plot of the gradient. Thank you

Answer 1

[Star Strider]

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

[Prince Alex]

Thats the problem it shows the resultant gradient using arrows only. Unfortunately I am looking for a contourf plot of the gradient. Thank you.

[Star Strider]

I am not certain what you want.

This uses the example from the gradient documentation to create the gradient vectors, and contourf to plot their sum:

x = -2:0.2:2;
y = x';
z = x .* exp(-x.^2 - y.^2);
[px,py] = gradient(z);

figure
contourf(px+py)

figure
meshc(px+py)

The meshc plot simply gives another view of the result to clarify it.

[Prince Alex]

Thank you. I think it will work. But the above script is showing matrix dimension error. Thank you so much

[Star Strider]

My pleasure!

It should not be showing any error. It is an example from the documentation (that I linked to in my oridginal Answer), and ran for me without error in R2020b. The ‘px’ and ‘py’ matrices are both (21x21), so the addition should work. If it is not working with your code, please post it.

Answer 2

[KSSV]

M = sqrt(U.^2+W.^2) ; 
contour(X,Y,M)

[Prince Alex]

Its a nice way. But since it is electric field it will have both positive and negative values. Squaring results in absolute value. @ KSSV a simple U + W will give the answer?