finding area under curve by using nth number of trapezoid

Hi so i have to find the inegral of a function f over a given interval with a user specified number of trapezoids n

this is the function that i have come up with

function Q = trapz( a,b,n )

h = (b-a)/n;

x = a: h: b;

Q = 0;

for i= 0:1:n

Q = Q + 2*func (x(i));

end

Q = Q+f(x(1));

Q = Q + f((x(n+1)));

Q = Q* h/2;

end

I also defin func (x(i)) as

function value = func(xi)

value = sin (xi);

end

however when i run the code it said array indices must be positive integer or logical value, What does this mean, and how can i fix it? thank you

Answer 1

[David Hill]

You can pass a function into a function.

f=@(x)sin(x);
function A = trapz(a,b,n,f)
x=linspace(a,b,n+1);
h=(b-a)/n;
A=0;
for i=1:n
    A=A+.5*(f(x(i))+f(x(i+1)))*h;
end
end