I need to take my trapezoid rule code and adjust it keeping the same format to sole for the Simpson rule. I am just no sure how to get this done. I have tried this and keep getting errors. Here is my trapezoid code. Thank You so much!

function s = myTrap(f,a,b,n)

x = linspace(a,b,n+1); %for n trapezoids, use n+1 points

h = (b-a)/n; s = (f(a)+f(b))/2; %initialize sum

%trap sum

for i = 2:n s = s + f(x(i));

end s = s*h; %multiply sum by h

when f= @(x)sqrt(1+x^3) from 1-4 with 20 traps I get 12.875041 for simpson the same function 1-4 should output 12.871490