Error: Not enough input arguments

I have the following error in my Runge-Kutta (4 stage) function:

Not enough input arguments.

Error in RK4
for j = 2:N-1 % ERROR HERE

Error in EulerMUSCL (line 94)
        [U_RK] = RK4( U_T, Res, dx, dt, k);
        

My function:

function [ U_RK ] = RK4( U_T, Res, dx, dt, k,N )

%This function returns the consvar and applies 4th order RK. 

U_RK = U_T;% size is 8 by 1001 (8 by N)
a = zeros(4,1);
a(1) = 0.25;
a(2) = 1.0/3.0;
a(3) = 0.5;
a(4) = 1.0;   
for j = 2:N-1 %ERROR HERE
    U_RK(:,j) = U_T(:,j)-a(k)*dt*Res/(dx);
end
end

Why does it say not enough inputs?? Thanks

Answer 1

[per isakson]

Accourding to the definition

function [ U_RK ] = RK4( U_T, Res, dx, dt, k, N )

requires six input values. Your call of the function, RK4

[U_RK] = RK4( U_T, Res, dx, dt, k);

provides only five input values. A value for the last, N, is missing.

[Jamie Al]

Thanks, this definitely was the problem. Now I am having the following error:

Index exceeds the number of array elements (4).

Error in RK4 (line 19)
    U_RK(:,j) = U_T(:,j)-a(k)*dt*Res/(dx);

Error in EulerMUSCL (line 94)
        [U_RK] = RK4( U_T, Res, dx, dt,N, k);

k here i 4 because it's a 4 stage RK.

[per isakson]

This script returns a <8x100 double>; i.e. it doesn't throw an error.

%%
N = 1e2;
UT = randn( 8, N );
U_RK = RK4( UT, 1, 1e-2, 1e-2, 4, N );

Let me guess, you have switch the order between the inputs k and N. Compare the function declaration and your call-statement.

function [ U_RK ] = RK4( U_T, Res, dx, dt, k, N )
[U_RK] = RK4( U_T, Res, dx, dt,N, k);