Hi When I run my code I got an error message "Invalid expression. Check for missing or extra characters" for my if loop. I am not sure why. Someone there can help me?

% Define the velocity components

u

= @(x, y, t) 0;

v

= @(x, y, t) 2*y + 2*y*cos(t);

% 1) Plot streamlines at two instants of time

figure

;

[x, y] = meshgrid(-5:0.5:5, -5:0.5:5);

% First instant of time (t1)

t1

= 0;

streamline(x, y, u(x, y, t1), v(x, y, t1), 0, 0);

hold on

;

% Second instant of time (t2)

t2

= 2;

streamline(x, y, u(x, y, t2), v(x, y, t2), 0, 0);

title('Streamlines at Two Instants of Time');

xlabel('X-axis');

ylabel('Y-axis');

grid on

;

axis equal

;

when i running this why it is not showing stream lines in gaph only plan graph is coming after run

Answer 1

[Steven Lord]

u1 = @(x, y, t) 0

u1 = function_handle with value:
    @(x,y,t)0

u2 ... 
= @(x, y, t) 0

u2 = function_handle with value:
    @(x,y,t)0

% u3
% = @(x, y, t) 0

Don't split the code among multiple lines (as u1), or if you do use an ellipsis to continue the expression onto the next line (as u2).

I'm a bit confused why your question says you have a loop, since your code doesn't contain any of the looping keywords.