Why do I receive "Not enough input arguments"? or How can I better code this ODE?

I am trying to code

function dydt = myODE(t,y, r);

global P0 h0 r0 r1 r2 d3 p1 p2

P0=0.7;

h0=0.0000235;

r0=0.01818;

r1=0.08712;

r2=8.0217;

d3=0.1;

p1=0.4783;

p2=0.4987;

% y(1) = x_0;

% y(2) = x_1;

% y(3) = x_2;

% y(4) = x_3;

p0=P0./(1+h0.*y(1));

tmp1 = r0.*y(1).*(p0-1);

tmp2 = 2.*ro.*y(1).*(1-p0) + r1.*y(2).*(2.*p1-1);

tmp3 = 2.*r1.*y(2).*(1-p1) + r2.*y(2).*(2.*p2-1);

tmp4 =2.*r2.*y(3).*(1-p2) - d3.*y(4);

dydt = [tmp1; tmp2; tmp3; tmp4];

end

function exitflag = HematopoeiticSystemTrial

time = [0:1:4];

%------%

x_0 = 1/110;

x_1 = 1/24;

x_2 = 1/22;

x_3 = 1/10;

%------%

% ----- Paremeters -----%

global P0 h0 r0 r1 r2 d3 p1 p2

p = [x_0 x_1 x_2 x_3];

%--------------------------------------------------%

[t,dydt1] = ode45(@myODE,time,[p(1),p(2),p(3),p(4)],[],p);

dydt1

end

What could I be doing wrong?

Answer 1

[Dyuman Joshi]

I'm not sure why you receive that error, but your code works properly with some tweaks.

There is no need to use global here.

If you are defining the call to ode inside a function you need to assign variables as output and call that function accordingly.

Note that as you have defined a discrete Time span, thus the result be obtained for those particular values.

[T,Y]=HematopoeiticSystemTrial

T = 5×1

0 1 2 3 4

Y = 5×4

0.0091 0.0417 0.0455 0.1000 0.0090 0.0416 0.0484 0.4497 0.0090 0.0415 0.0513 0.7885 0.0089 0.0415 0.0542 1.1172 0.0089 0.0414 0.0571 1.4370

Here, the first column of the output Y corresponds to x_0, second to x_1, third to x_2 and fourth to x_3.

function [t,dydt1] = HematopoeiticSystemTrial
time = [0:1:4];
%------%
x_0 = 1/110;
x_1 = 1/24;
x_2 = 1/22;
x_3 = 1/10;
% ----- Paremeters -----%
p = [x_0 x_1 x_2 x_3];
%--------------------------------------------------%
[t,dydt1] = ode45(@myODE,time,p);
end

function dydt = myODE(t,y, r);
P0=0.7; 
h0=0.0000235;
r0=0.01818;
r1=0.08712;
r2=8.0217; 
d3=0.1;
p1=0.4783;
p2=0.4987; 
% y(1) = x_0;
% y(2) = x_1;
% y(3) = x_2;
% y(4) = x_3;
p0=P0./(1+h0.*y(1));
tmp1 = r0.*y(1).*(p0-1);
tmp2 = 2.*r0.*y(1).*(1-p0) + r1.*y(2).*(2.*p1-1);
tmp3 = 2.*r1.*y(2).*(1-p1) + r2.*y(2).*(2.*p2-1);
tmp4 =2.*r2.*y(3).*(1-p2) - d3.*y(4);
dydt = [tmp1; tmp2; tmp3; tmp4];
end

Answer 2

[Davide Masiello]

Here's a correct version of your code.

1) Time span and initial conditions must be in the same file as the ode solver, not sure why you embedded them in the exitflag function

tspan = [0,4];
x0 = [1/110 1/24 1/22 1/10];

2) I suggest you pass the extra parameters using function handling rather than gloval variables, it's a more robust approach.

P0=0.7; 
h0=0.0000235;
r0=0.01818;
r1=0.08712;
r2=8.0217; 
d3=0.1;
p1=0.4783;
p2=0.4987; 
[t,y] = ode45(@(t,y)myODE(t,y,P0,h0,r0,r1,r2,d3,p1,p2),tspan,x0);
plot(t,y)

function dydt = myODE(t,y,P0,h0,r0,r1,r2,d3,p1,p2);
p0=P0/(1+h0*y(1));
tmp1 = r0*y(1)*(p0-1);
tmp2 = 2*r0*y(1)*(1-p0)+r1*y(2)*(2*p1-1);
tmp3 = 2*r1*y(2)*(1-p1)+r2*y(2)*(2*p2-1);
tmp4 = 2*r2*y(3)*(1-p2)-d3*y(4);
dydt = [tmp1; tmp2; tmp3; tmp4];
end

Answer 3

[Sachin]

Hi @Chiara,

I understand that you are getting error ‘ Not enough input argument’. Here are some points that might be helpful to you :

1. ‘MyODE' function should be below to the ‘ HematopoeiticSystemTrial’ function. Because MATLAB scans the code from the first line so it doesn’t find inputs to the function ‘ HematopoeiticSystemTrial’’. So place ‘myODE’ function below.

function exitflag = HematopoeiticSystemTrial
time = [0:1:4];
%------%
x_0 = 1/110;
x_1 = 1/24;
x_2 = 1/22;
x_3 = 1/10;
%------%
% ----- Paremeters -----%
global P0 h0 r0 r1 r2 d3 p1 p2
p = [x_0 x_1 x_2 x_3];
%--------------------------------------------------%
[t,dydt1] = ode45(@myODE,time,[p(1),p(2),p(3),p(4)],[],p);
dydt1
end


function dydt = myODE(t,y, r);
global P0 h0 r0 r1 r2 d3 p1 p2
P0=0.7; 
h0=0.0000235;
r0=0.01818;
r1=0.08712;
r2=8.0217; 
d3=0.1;
p1=0.4783;
p2=0.4987; 
% y(1) = x_0;
% y(2) = x_1;
% y(3) = x_2;
% y(4) = x_3;
p0=P0./(1+h0.*y(1));
tmp1 = r0.*y(1).*(2*p0-1);
tmp2 = 2.*r0.*y(1).*(1-p0) + r1.*y(2).*(2.*p1-1);
tmp3 = 2.*r1.*y(2).*(1-p1) + r2.*y(2).*(2.*p2-1);
tmp4 =2.*r2.*y(3).*(1-p2) - d3.*y(4);
dydt = [tmp1; tmp2; tmp3; tmp4];
end

2. Check your equation of tmp1,tmp2,tmp3,tmp4 . Your tmp1 equation doesn't seems to be correct.

3. You can find more details about Parameterizing function here :

https://www.mathworks.com/help/matlab/math/parameterizing-functions.html