I want to solve it with the unknown

clc,clear;close all;

syms r Nddotmax;

f = @(t,y,s,r,Nddotmax) (r*((1-y)/Nddotmax)+s-0.0012*0.02*y); %y=Nddotexi,vmed=0.02,fdot=3*10^(-18),r=0.0012,s=Nsurv

a = 0; %input('initial ponit, a: ');

b = 100; %input('end point, b: ');

n = 10; %input('intervals, n: ');

alpha = 0; %input('initial condition, alpha: ');

h = (b-a)/n;

t=[a zeros(1,n+1)];

y=[alpha zeros(1,n+1)];

s=[0 zeros(1,n+1)];

for i = 1:n+1

t(i+1)=t(i)+h;

yprime=y(i)+h*f(t(i),y(i),s(i)); %slope

y(i+1)=y(i)+h*f(t(i+1),yprime,s(i+1));

fprintf('%.4f %.4f\n', t(i), y(i));

figure(1)

plot(t,y,'r-o');

xlabel('t values'); ylabel('y values');

grid on; hold on;

legend('y')

end

But there is a problem that input is not enough(Insufficient input arguments.)

then how can i fix it?

Answer 1

[Dyuman Joshi]

You have defined your function handle as -

f = @(t,y,s,r,Nddotmax) (r*((1-y)/Nddotmax)+s-0.0012*0.02*y);

Which means it requires 5 inputs to give you an output. Though 't' isn't mentioned in the expression, so either remove it or check the expression again.

But you are only calling it with 3 inputs, that is why it is giving the error

yprime=y(i)+h*f(t(i),y(i),s(i)); %slope
y(i+1)=y(i)+h*f(t(i+1),yprime,s(i+1))

To fix the problem, call your function handle with 5 input.

Also, defining syms variable is redundant as you are using a function handle.