Why is it always showing an error as phi is an undefined function for input argument type char ??

U = 1; % Uniform stream % GRID: x = -2:.02:2; y = -2:.02:2; for m = 1:length(x) for n = 1:length(y) xx(m,n) = x(m); yy(m,n) = y(n); % Velocity potential function: phi UniFlow(m,n) = U * x(m); % Stream function: psi UniFlow(m,n) = U * y(n); end end % Plots % Uniform stream in x direction: contour(xx,yy,psi UniFlow,[-2:.5:2],’k’),hold on contour(xx,yy,phi UniFlow,[-10:1:5],’r’) axis image,hold off title(’Uniform stream in x direction’) xlabel(’x’),ylabel(’y’)

Answer 1

[Mischa Kim]

Sofiya, in your code above some of the variable names contain empty spaces (if the copy-paste worked), which is not valid. E.g.

 phi UniFlow

needs to be changed to, e.g.,

 phi_UniFlow

Check out:

 U = 1; % Uniform stream % GRID:
 x = -2:.02:2;
 y = -2:.02:2; 
 for m = 1:length(x) 
    for n = 1:length(y) 
        xx(m,n) = x(m); 
        yy(m,n) = y(n); % Velocity potential function: 
        phi_UniFlow(m,n) = U * x(m); % Stream function:
        psi_UniFlow(m,n) = U * y(n); 
    end
 end % Plots % Uniform stream in x direction: 
 contour(xx,yy,psi_UniFlow,[-2:.5:2],'k'),
 hold on 
 contour(xx,yy,phi_UniFlow,[-10:1:5],'r') 
 axis image
 hold off 
 title('Uniform stream in x direction') 
 xlabel('x')
 ylabel('y')

Answer 2

[Sofiya]

Thank u