A function without any argument

Hello everyone,

Could someone help me to understand why I got this error while running my script :

>> shoot4nl
Not enough input arguments.

My script is the following :

function shoot4nl

% Shooting method for nonlinear 4th-order boundary
% value problem 

global XSTART XSTOP H  % Make these params. global.
XSTART = 0; XSTOP = 1; % Range of integration.
H = 0.1;               % Step size.
freq = 1;              % Frequency of printout.
u = [-1 1];            % Trial values of u(1)
                       % and u(2).

x = XSTART;
u = newtonRaphson2(@residual,u);
[xSol,ySol] = runKut5(@dEqs,x,inCond(u),XSTOP,H);
printSol(xSol,ySol,freq)

function F = dEqs(x,y)    % Differential equations.
F = zeros(1,4);
F(1) = y(2); F(2) = y(3); F(3) = y(4);
if x < 10.0e-4; F(4) = -12*y(2)*y(1)^2;
else;           F(4) = -4*(y(1)^3)/x;
end


function y = inCond(u)    % Initial conditions; u(1)
y = [0 0 u(1) u(2)];      % and u(2) are unknowns.


function r = residual(u)  % Bounday residuals.
global XSTART XSTOP H
r = zeros(length(u),1);
x = XSTART;
[xSol,ySol] = runKut5(@dEqs,x,inCond(u),XSTOP,H);
lastRow = size(ySol,1);
r(1) = ySol(lastRow,3);
r(2) = ySol(lastRow,4) - 1;

I am trying to implement a shooting method algorithm for solving a non-linear equation.

Thank you for your help,

Best regards.

[Torsten]

Why not using bvp4c ?

[Wissem]

@Torsten Thank you for your reply : I didn't know about this function and I will surely look for it. However, I would also like to understand why this one is not working since I am trying to implement it. Thanks in advance.

[Torsten]

Did you save shoot4nl as "shoot4nl.m" in your working directory and now call it from a script named "shoot.m", e.g. ?

The other functions called (newtonRaphson2, runKut5) are also in this directory ?

[Jan]

Please post the complete errort message. In Which line does this error occur?

When I rund your code, I get a message about the missing "newtonRaphson2" function.

[Wissem]

Yes, I did save the function as "shoot4nl.m" in the directory. Is there something wrong with calling this function from a new script ?

[Wissem]

@Torsten@Jan This is the complete error obtained :

>> shoot4nl
Not enough input arguments.

Error in runKut5 (line 53)
    if e <= eTol

Error in shoot4nl>residual (line 34)
[xSol,ySol] = runKut5(@dEqs,x,inCond(u),XSTOP,H);

Error in newtonRaphson2>jacobian (line 35)
f0 = feval(func,x);

Error in newtonRaphson2 (line 19)
    [jac,f0] = jacobian(func,x);

Error in shoot4nl (line 14)
u = newtonRaphson2(@residual,u);

I wille edit my post to share the other functions in order to run properly what I wrote.

Thanks

[Jan]

Fine. This is useful. The problem occurs inside "runKut5". Most likely this function expects more inputs, than you provide in:

[xSol,ySol] = runKut5(@dEqs,x,inCond(u),XSTOP,H);

Please post the code of the failing function. What is "e" and "eTol"?

Answer 1

[Voss]

There is a line in runKut5 that looks like it accidentally got commented out due to a comment on the previous line:

if nargin < 6; eTol = 1.0e-6; end

This line sets eTol to 1e-6 if it is not given as an input argument (it is the 6th input). Your calling function calls runKut5 with 5 inputs, so making this change should avoid the error. Updated runKut5.m is attached here.

[Wissem]

@_ Thank you for your help : it worked now. I didn't pay attention to this line : thanks !

[Voss]

You're welcome!