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Error RungeKutta method......not enough input arguments

Asked by Camilo Sánchez on 10 Nov 2017
Latest activity Commented on by Camilo Sánchez on 10 Nov 2017
function [xSol,ySol] = runKut4(dEqs,x,y,xStop,h)
%function [xSol,ySol] = runKut4(dEqs,x,y,xStop,h)
% 4th-order Runge--Kutta integration.
% USAGE: [xSol,ySol] = runKut4(dEqs,x,y,xStop,h)
% INPUT:
% dEqs = handle of function that specifies the 1st-order differential equations
% F(x,y) = [dy1/dx dy2/dx dy3/dx ...].
% x,y = initial values; y must be row vector.
% xStop = terminal value of x.
% h = increment of x used in integration.
% OUTPUT:
% xSol = x-values at which solution is computed.
% ySol = values of y corresponding to the x-values.
if size(y,1) > 1;
y = y';
end % y must be row vector
xSol = zeros(2,1);
ySol = zeros(2,length(y));
xSol(1)= x;
ySol(1,:)=y;
i = 1;
while x < xStop
i = i + 1;
h = min(h,xStop - x);
K1 = h*feval(dEqs,x,y);
K2 = h*feval(dEqs,x + h/2,y + K1/2);
K3 = h*feval(dEqs,x + h/2,y + K2/2);
K4 = h*feval(dEqs,x+h,y + K3);
y = y + (K1 + 2*K2 + 2*K3 + K4)/6;
x = x + h;
xSol(i) = x;
ySol(i,:) = y; % Store current soln.
end
-------------------------------------------------------------------------
function F = fex7_4(x,y)
% Differential. eqs. used in Example 7.4
F = zeros(1,2);
F(1) = y(2); F(2) = -0.1*y(2) - x;
[x,y] = runKut4(@fex7_4,0,[0 1],2,0.25);
printSol(x,y,1)
--------------------------------------------------------------
>> fex7_4 Error using fex7_4 (line 4) Not enough input arguments.
not enough input arguments ??????

  3 Comments

Please show us exactly how you are calling your function (i.e., give us the inputs), and then copy & paste the entire error message for us to see.
Upss sorry....here is:
[x,y] = runKut4(@fex7_4,0,[0 1],2,0.25);
printSol(x,y,1)
>> fex7_4 Error using fex7_4 (line 5) Not enough input arguments.

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1 Answers

Answer by Mischa Kim
on 10 Nov 2017
Edited by Mischa Kim
on 10 Nov 2017
 Accepted Answer

Store runKut4 and fex7_4 in separate m-files and then execute
[x,y] = runKut4(@fex7_4,0,[0 1],2,0.25);
e.g. in the MATLAB command window and you should get results for x and y. printSol is probably another function you have access to, I do not know. But you could simply use plot to plot the solution trajectory.

  1 Comments

Thanks friend, I found the problem and the other function.

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