Error: Not enough input arguments

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Jamie Al
Jamie Al 2021-5-2
编辑： per isakson 2021-5-2
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

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per isakson
per isakson 2021-5-2
编辑：per isakson 2021-5-2
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.
  2 个评论
Jamie Al
Jamie Al 2021-5-2
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
per isakson 2021-5-2
编辑：per isakson 2021-5-2
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);

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