Index exceeds the number of array elements (6) (I´m doing the program for composite simpson 3/8 rule)

r = mod(n,3);
if (r ==0)
    n = n;
end

x = linspace(alfa,beta,n)';
%evaluamos la función en los puntos de la partición x
f = zeros(n,1);
for k = 1:n
    f(k) = feval(fx,x(k));
end

h = x(4)-x(1);
Ix = 0;

% n es multiplo de 3 / n = 3*m / #de subintercalos es: (n)/3 = m.
m = floor(n/3);

for j = 1:m
    ind1 = 3*(j-1)+1; ind2 = 3*j-1; ind3 = 3*j; ind4 = 3*j+1;
    Ix = Ix + ((3*h)/8)*(f(ind1)+3*f(ind2)+3*f(ind3)+f(ind4));
end

end

[Sindar]

Please copy the full error text.

Also, what's the point of this block?

if (r ==0)
    n = n;
end

The only effect would be that the code might throw an 'n is undefined' error when r=0 and leaves it for later if not

[Ivonne Márquez Delgado]

Index exceeds the number of array elements (6).

Error in misimpson38 (line 36)

Ix = Ix + ((3*h)/8)*(f(ind1)+3*f(ind2)+3*f(ind3)+f(ind4));

Error in prueba_misimpson38 (line 12)

[Ix] = misimpson38(fx,alfa,beta,n);

I tried to use that as n= n+1 so it would count the 4th element, but the answer was wrong

Answer 1

[Cris LaPierre]

The error generally means you are trying to extract a value of an element of a vector that does not exist. Here, your vector is f and one of your indices (ind1-4) contains a value greater than the length of f (which is 6).

f = [1 2 3 4 5 6]

f = 1×6

1 2 3 4 5 6

●

f(10)

Index exceeds the number of array elements (6).