Error: Not enough input arguments

Hi! I'm trying to run the command from https://la.mathworks.com/help/optim/ug/fit-ode-problem-based-least-squares.html and I have a problem when I run the script:

>> diffun

Not enough input arguments.

Error in diffun (line 3)

s12 = y(1)*y(2);

function dydt = diffun(~,y,r)

dydt = zeros(6,1);

s12 = y(1)*y(2);

s34 = y(3)*y(4);

dydt(1) = -r(1)*s12;

dydt(2) = -r(1)*s12;

dydt(3) = -r(2)*s34 + r(1)*s12 - r(3)*s34;

dydt(4) = -r(2)*s34 - r(3)*s34;

dydt(5) = r(2)*s34;

dydt(6) = r(3)*s34;

r = [2.5 1.2 0.45];

y0 = [1 1 0 1 0 0];

tspan = linspace(0,5);

soltrue = ode45(@(t,y)diffun(t,y,r),tspan,y0);

yvalstrue = deval(soltrue,tspan);

for i = 1:6

subplot(3,2,i)

plot(tspan,yvalstrue(i,:))

title(['y(',num2str(i),')'])

end

end

I'm new to using matlab, I'd appreciate any help.

Thanks!

Answer 1

[Torsten]

r = [2.5 1.2 0.45];
y0 = [1 1 0 1 0 0];
tspan = linspace(0,5);
soltrue = ode45(@(t,y)diffun(t,y,r),tspan,y0);
yvalstrue = deval(soltrue,tspan);
for i = 1:6
    subplot(3,2,i)
    plot(tspan,yvalstrue(i,:))
    title(['y(',num2str(i),')'])
end

function dydt = diffun(~,y,r)
dydt = zeros(6,1);
s12 = y(1)*y(2);
s34 = y(3)*y(4);
dydt(1) = -r(1)*s12;
dydt(2) = -r(1)*s12;
dydt(3) = -r(2)*s34 + r(1)*s12 - r(3)*s34;
dydt(4) = -r(2)*s34 - r(3)*s34;
dydt(5) = r(2)*s34;
dydt(6) = r(3)*s34;
end

[Laureana]

Thanks @Torsten! I just had to change the name of the function because it was the same in the script and it works!