Numerical evaluation of an integral, low order method.
Q = QUAD('f',a,b) approximates the integral of f(x) from a to b
to within a relative error of 1e-3. 'f' is a string
containing the name of the function. Function f must return a
vector of output values if given a vector of input values.
Q = QUAD(F,a,b,tol) integrates to a relative error of tol.
Q = Inf is returned if an excessive recursion level is reached,
indicating a possibly singular integral.
Q = QUAD(F,a,b,tol,trace) integrates to a relative error of tol and
traces the function evaluations with a point plot of the integrand.
QUAD uses an adaptive recursive Simpson's rule.
See also QUAD8HSRNMC.