Not enough input arguments using ode45

I'm trying to simulate a non linear prey-predator system using ode45, but I'm pretty new to Matlab functions and keep getting errors.

close; clear;

timerange = [0 20];
IC=[1; 1; 1; 1];
r = [1 0.72 1.53 1.27];
a = [1 1.09 1.52 0; 
     0 1 0.44 1.36;
     2.33 0 1 0.47;
     1.21 0.51 0.35 1];
IC=[1 1 1 1];
fun = @(t, x)predapredatore(x, r, a);
[t, x]=ode45(predapredatore,timerange,IC);

Not enough input arguments.

Error in solution>predapredatore (line 18)
dx= [r(1)*x(1)*(1 - a(1,1)*x(1) - a(1,2)*x(2) - a(1,3)*x(3) - a(1,4)*x(4));...

plot(t, x)


function dx=predapredatore(x, r, a)
dx= [r(1)*x(1)*(1 - a(1,1)*x(1) - a(1,2)*x(2) - a(1,3)*x(3) - a(1,4)*x(4));...
     r(2)*x(2)*(1 - a(2,1)*x(1) - a(2,2)*x(2) - a(2,3)*x(3) - a(2,4)*x(4));...
     r(3)*x(3)*(1 - a(3,1)*x(1) - a(3,2)*x(2) - a(3,3)*x(3) - a(3,4)*x(4));...
     r(4)*x(4)*(1 - a(4,1)*x(1) - a(4,2)*x(2) - a(4,3)*x(3) - a(4,4)*x(4));];
end

The errors I get are:

Not enough input arguments.

Error in preypredator>predapredatore (line 28)
dx= [r(1)*x(1)*(1 - a(1,1)*x(1) - a(1,2)*x(2) - a(1,3)*x(3) - a(1,4)*x(4));...

Error in preypredator (line 13)
[t, x]=ode45(predapredatore,timerange,IC);

Where am I missing input arguments? And what type of errors are in line 28 and 13?

Answer 1

[Star Strider]

You already did everything necessary. Just change the ode45 call to:

[t, x]=ode45(fun,timerange,IC);

and it works —

close; clear;

timerange = [0 20];
IC=[1; 1; 1; 1];
r = [1 0.72 1.53 1.27];
a = [1 1.09 1.52 0; 
     0 1 0.44 1.36;
     2.33 0 1 0.47;
     1.21 0.51 0.35 1];
IC=[1 1 1 1];
fun = @(t, x)predapredatore(x, r, a);
[t, x]=ode45(fun,timerange,IC);

plot(t, x)

function dx=predapredatore(x, r, a)
dx= [r(1)*x(1)*(1 - a(1,1)*x(1) - a(1,2)*x(2) - a(1,3)*x(3) - a(1,4)*x(4));...
     r(2)*x(2)*(1 - a(2,1)*x(1) - a(2,2)*x(2) - a(2,3)*x(3) - a(2,4)*x(4));...
     r(3)*x(3)*(1 - a(3,1)*x(1) - a(3,2)*x(2) - a(3,3)*x(3) - a(3,4)*x(4));...
     r(4)*x(4)*(1 - a(4,1)*x(1) - a(4,2)*x(2) - a(4,3)*x(3) - a(4,4)*x(4));];
end

.