Requires more input arguments to run

I just bought MatLab for a school project a few hours ago, and I've never used this software before. I need to run the code my professor has posted, but the message "'convection_hat' requires more input arguments to run" comes up. Is there something wrong with the code she posted? I'd really appreciated any help, as I'm totally lost at the moment. Here is the code:

function d_theta_hat = convection_hat( t, theta_hat_vec )
  global F N tol del_x del_y lap_inv;

    % theta_hat = Fourier transform of Theta given in ODE call.
    % t = time
    % return Fourier Transform of -u \cdot \grad theta 
    % where v = -\lap \inv P ( \theta \cdot \grad \inv \theta )
    % and u = v / \norm{\grad v}_{L^2}

    theta_hat = reshape( theta_hat_vec, N, N );

    % g = \theta \grad\inv \theta
    % To convolve accurately we need to "circularly" convolve, which matlab
    % doesn't have in 2D. Instead we ifft, multipliy and fft back.
    linv_theta_hat = lap_inv .* theta_hat;
    theta = ifft2( theta_hat, 'symmetric' );
    g_hat(:, :, 1) = fft2( theta .* ifft2( del_x .* linv_theta_hat, 'symmetric' ) );
    g_hat(:, :, 2) = fft2( theta .* ifft2( del_y .* linv_theta_hat, 'symmetric' ) );

    % div_g_hat = (\divergence g)^\hat
    div_g_hat = del_x .* g_hat(:, :, 1) + del_y .* g_hat( :, :, 2 );

    % v = -\lap\inv P g
    v_hat(:, :, 1) = -lap_inv .* ( g_hat(:,:,1) - del_x .* lap_inv .* div_g_hat );
    v_hat(:, :, 2) = -lap_inv .* ( g_hat(:,:,2) - del_y .* lap_inv .* div_g_hat );

    v_hat_norm1 = del_x.*v_hat(:,:,1);
    v_hat_norm2 = del_x.*v_hat(:,:,2);
    v_hat_norm3 = del_y.*v_hat(:,:,1);
    v_hat_norm4 = del_y.*v_hat(:,:,2);

    norm_v_hat = sqrt( norm( v_hat_norm1(:), 2 )^2 + ...
  norm( v_hat_norm2(:), 2 )^2 + norm( v_hat_norm3(:), 2 )^2 + ...
  norm( v_hat_norm4(:), 2 )^2 );
    norm_v = norm_v_hat / N^2; % L2 conversion factor for DFT.

    % Compare norm_v relative to norm_g
    linv_g_hat( :, :, 1 ) = lap_inv .* g_hat(:, :, 1);
    linv_g_hat( :, :, 2 ) = lap_inv .* g_hat(:, :, 2);
    norm_linv_g = norm( linv_g_hat(:), 2 ) / N^2;

    if norm_v < norm_linv_g *tol;
  disp( sprintf( ...
      'Possible saddle point: t=%.3f, norm_v=%.9f, norm_g=%.9f', ...
      t, norm_v, norm_linv_g ) );
    end

    u(:, :, 1) = F*ifft2( v_hat(:, :, 1), 'symmetric' ) / norm_v;
    u(:, :, 2) = F*ifft2( v_hat(:, :, 2), 'symmetric' ) / norm_v;

    d_theta_hat = -fft2( ...
  u(:,:,1) .* ifft2( del_x.*theta_hat, 'symmetric' ) + ...
  u(:,:,2) .* ifft2( del_y.*theta_hat, 'symmetric' ) );

    % Finally we need our output to be used in ode23 or ode45 functions, so we
    % need reshape it.
    d_theta_hat = d_theta_hat(:);
end

[per isakson]

Exactly how did you try to run the function, convection_hat. Don't let us guess!

[Adam]

I'm sorry, but I'm not exactly sure what you mean. I'm not familiar at all with how this software works, but I just clicked the green "run" button and the message "convection_hat requires more input arguments to run: convection_hat(t, theta_hat_vec)." I apologize. I'm not sure if I've clarified anything.

[per isakson]

Your professor obviously chose not to make it that simple for you. Didn't she provide some additionally instruction?

See Run Functions in the Editor and run study the examples.

Answer 1

[Hikaru]

What did you type before you get that error message? You need to define the values for t and theta_hat_vec

[Adam]

Oh, I see. Again, I'm sorry for asking such a trivial thing, but under the "Run" button, where it says "type code to run", I entered something like convection_hat(5,5), for example. I tried this, but now a new message comes up saying "Syntax error, convection_hat cannot run as it appears"

[Hikaru]

I think the second input argument, theta_hat_vec, should be a vector. Is this the only code provided by your professor? Maybe you could re-read the assignment and see if she mentioned how to find the values for theta hat.

[Adam]

Yes, unfortunately this is the only code provided. There also seems to be a problem when I try running it as convection_hat(5,[,5 5]), which from what I've read, is how you'd right a vector in Matlab. Thank you for your help though. Much appreciated!

[Hikaru]

Technically, you also need to know the values for the global variables (F, N, tol, del_x, del_y, and lap_inv) before this code could run.

Good luck with the school project.