Too many input arguments: error in ODE45

I have the following coefficient matrix my_Xi:

my_Xi =

0         0         0         0         0         0
0         0         0         0         0         0
0   11.3936         0         0         0         0
0         0         0         0         0         0
0   15.7629         0         0         0         0
0  -15.4752         0         0         0         0
0         0         0         0         0         0
0         0         0         0         0         0
0   49.6849         0  -27.7503   17.9319   10.0351
0         0         0         0         0         0
0         0         0         0         0         0
0  -18.1205   12.0592   28.3871         0         0
0         0         0         0         0         0
0         0         0  -39.3697         0         0
0   55.9200         0         0   26.7242         0
0         0  -19.7125  -43.3555         0         0
0         0         0   80.7743         0         0
0         0         0         0         0         0
0         0         0   17.6067         0         0
0  -15.4446  -23.2459         0         0         0
0  -42.8207         0         0  -21.9576         0
0   20.2546         0  -39.3216         0         0
0   64.4836         0  -22.1828   16.8531         0
0  -23.5016   32.6644   60.2232         0         0
0   45.2034   20.2962         0   18.9374         0
0         0         0  -43.7764         0         0
0         0         0         0         0         0
0  -21.5528         0   23.3698         0         0

I am trying to solve a system of odes with 6 variables:

my_n = 6
my_x0 = [-0.4999;0.2927;-1.8887;-0.8495;-0.4719;-1.4219]
fun = @(x) my_Xi.'* [1, x(1), x(2), x(3), x(4), x(5), x(6), x(1)*x(1), x(1)*x(2), x(1)*x(3), x(1)*x(4), x(1)*x(5), x(1)*x(6), x(2)*x(2), x(2)*x(3), x(2)*x(4), x(2)*x(5), x(2)*x(6), x(3)*x(3), x(3)*x(4), x(3)*x(5), x(3)*x(6), x(4)*x(4), x(4)*x(5), x(4)*x(6), x(5)*x(5),x(5)*x(6), x(6)*x(6)]
options = odeset('RelTol',1e-12,'AbsTol',1e-12*ones(1,my_n));
my_dt = 0.0083; 
my_tspan=[.01:my_dt:(1133)*my_dt];

[t,x]=ode45(fun, my_tspan, my_x0, options);

However, this code gives me the error: "Too many input arguments." Can someone please help?

Answer 1

[Paul]

Hi Shreshtha,

The function handle input to ode45 needs to take two arguments: t and x. Also, the matrix multiply defined in fun won't work, I'm guessing the vector needs to be transposed to make it compatible wity my_Xi.'.

Code below runs without error.

my_Xi = [
0         0         0         0         0         0
0         0         0         0         0         0
0   11.3936         0         0         0         0
0         0         0         0         0         0
0   15.7629         0         0         0         0
0  -15.4752         0         0         0         0
0         0         0         0         0         0
0         0         0         0         0         0
0   49.6849         0  -27.7503   17.9319   10.0351
0         0         0         0         0         0
0         0         0         0         0         0
0  -18.1205   12.0592   28.3871         0         0
0         0         0         0         0         0
0         0         0  -39.3697         0         0
0   55.9200         0         0   26.7242         0
0         0  -19.7125  -43.3555         0         0
0         0         0   80.7743         0         0
0         0         0         0         0         0
0         0         0   17.6067         0         0
0  -15.4446  -23.2459         0         0         0
0  -42.8207         0         0  -21.9576         0
0   20.2546         0  -39.3216         0         0
0   64.4836         0  -22.1828   16.8531         0
0  -23.5016   32.6644   60.2232         0         0
0   45.2034   20.2962         0   18.9374         0
0         0         0  -43.7764         0         0
0         0         0         0         0         0
0  -21.5528         0   23.3698         0         0];

my_n = 6;
my_x0 = [-0.4999;0.2927;-1.8887;-0.8495;-0.4719;-1.4219];

% two corrections here
fun = @(t,x) my_Xi.'* [1, x(1), x(2), x(3), x(4), x(5), x(6), x(1)*x(1), x(1)*x(2), x(1)*x(3), x(1)*x(4), x(1)*x(5), x(1)*x(6), x(2)*x(2), x(2)*x(3), x(2)*x(4), x(2)*x(5), x(2)*x(6), x(3)*x(3), x(3)*x(4), x(3)*x(5), x(3)*x(6), x(4)*x(4), x(4)*x(5), x(4)*x(6), x(5)*x(5),x(5)*x(6), x(6)*x(6)].';

options = odeset('RelTol',1e-12,'AbsTol',1e-12*ones(1,my_n));
my_dt = 0.0083; 
my_tspan=[.01:my_dt:(1133)*my_dt];
[t,x]=ode45(fun, my_tspan, my_x0, options);

[Shreshtha Chaturvedi]

Hi, thank you! I am unable to accept your answer as it says: "Unable to complete the action because of changes made to the page. Reload the page to see its updated state", even after reloading. I will try again after some time :)