MATLAB error: too many input arguments

Hi, I'm trying to solve the variable length pendulum equation with ODE45

here are the codes:

-------------------------

%Pendulum of variable length: T is the period, th0 the initial conditions

%for the angulus and angular velocity, eta is the length parameter and g

%is the gravitational acceleration

%for the length law l(t) see 'el.m'

%for the motion equations see 'eq_varpend.m'

%usage: [t,th] = varpend

function [t,th] = varpend()

entries={
    'T',...
    'th0',...
    'eta',...
    'g',...
    };

default={
    '30*pi',...
    'pi/6',...
    '1.0',...
    '9.8',...
    };

setup = inputdlg(entries,'Variable length pendulum',1,default,'on');

T=str2num(setup{1});

th0=[str2num(setup{2}),0];

eta=str2num(setup{3});

g=str2num(setup{4});

opt=odeset('Abs',1e-10,'Rel',1e-10);

[t,th]=ode45('eq_varpend', [0,T], th0, opt, eta, g);

plot(t,th(:,1)); 

grid on

xlim([0 T])

title('Pendulum trajectory');

figure(2)

plot(th(:,1), th(:,2)); 

grid on

axis equal

title('Phase space');

------

%motion equation fot the v.l. pendulum

function dtheta = eq_varpend(t,th,eta,g)

[q,qdot] = el(t,eta);

dtheta = [ th(2) ; -g*sin(th(1))./q-2*th(2).*qdot./q; ]; 

------

%length law for the v.l. pendulum

function [q,qdot] = el(t,eta)

q = 1+eta*t;
qdot = eta;

------

When I type [t,th] = varpend I get the following error message:

Error using eq_varpend

Too many input arguments.

Can anyone help me? Thanks

Answer 1

[the cyclist]

I replaced your first argument to ode45 with the function handle @eq_varpend, and your code worked fine for me:

[t,th]=ode45(@eq_varpend, [0,T], th0, opt, eta, g);

Answer 2

[Enrico Picari]

It works for me too. Quite strange, in other codes the apostrophes did't return any error...

Anyway, great great thanks! It was driving me crazy!

[the cyclist]

Please consider "accepting" my answer, which may help future users who have similar questions. (Also, in the future, it would have made more sense to make your remark a "comment" on my answer, rather than a separate answer.)

[Enrico Picari]

Roger!

[dinesh reddy]

function [swav]=s_wav(x)
l=1;
x=x-l/6;
a=0.25;
b=15;
n=100;
s1=(a/(2*b))*(2-b);
s2=0; 
for i = 1:n   
harm3=(((2*b*a)/(i*i*pi*pi))*(1-cos((i*pi)/b)))*cos((i*pi*x)/l);    
s2=s2+harm3;
end
swav=-1*(s1+s2);
%%I generated the S wave of ecg signal by using the above code%%
%%By using below code i am running it and i was struck with an error called too many input arguments can any one help me%%
x=0.01:0.01:2;
default=input('press 2:\n');
  rate=input('\n\nenter the heart beat rate :');  
  li=30/rate; 
  fprintf('\n\ns wave specifications\n'); 
  a_swav=input('amplitude = ');    
  d_swav=input('duration = '); 
 swav=s_wav(x,a_swav,d_swav,t_swav,li);

[Walter Roberson]

You define s_wav as taking 1 single parameter. Your call s_wav(x,a_swav,d_swav,t_swav,li) tries to provide 5 parameters to s_wav . Your exising s_wav code does not even appear to have any place it could use those extra parameters.