Error using Quiver function

Hi, I am having an error using Quiver. Below is my code.

[X,Y] = meshgrid(-1:0.1:1, -1:0.1:1);
k=2*pi;
syms U_inf Lambda Psi X Y u v
Psi = U_inf*Y+((Lambda/k)*atan(Y/X));
u = diff(Psi,Y);
v = diff (Psi, X);
quiver (X,Y,u,v)

The error is "Unable to convert expression into double array."

I believe I am not using the syms correctly. Any help is appreciated!

Answer 1

[KSSV]

You cannot use like that. You need to take all data in double i.e in numbers to plot the arrows.Something like below:

[X,Y] = meshgrid(-1:0.1:1, -1:0.1:1);
k=2*pi;

U_inf = rand ; % define your value 
Lambda = 1. ;  %define your value 

Psi = U_inf*Y+((Lambda/k)*atan(Y./X));
u = gradient(Psi);
v = gradient(Psi);
quiver (X,Y,u,v)

[Bajinder Singh]

Thanks for the response. But I am not given any values for U_inf and Lambda. They are simply constants. That is why I was trying to use the "syms" command.