Trapezoidal rule in MATLAB

This is my code so far.

function v = velocity(x, route)

load route;

d = distance_km; 
y = speed_kmph;
dd=0:distance_km(end);

pp=spline(d,y);
v = ppval(pp, x);

plot(d,y,'ro');

    hold on
    h=fplot(@(x)ppval(pp,x),[d(1),d(end)], '- b')
    hold off

if (x<0 | x>d(end)) error ('Fel') end end

This is the given code that I'm supposed to use when using trapezoidal rule:

function T = trapets(func, a, b, n)

h=(b-a)/n;
x = linspace(a,b,n+1);
fx = func(v);
T = h*(sum(fx)-(fx(1)+fx(end))/2);
end

How does the trapezoidal rule work in MATLAB? I don't really know where to begin.

Answer 1

[Rava Sash]

Is there any more information I should give? I'm very new to programming.