**quad_trapezoid**,
a MATLAB code which
interactively applies a trapezoid quadrature rule using n intervals
to estimate the integral of a function f(x) over an interval [a,b].

The user enters a formula for f(x), the values of a and b, and the value of n.

The program sets up the trapezoid rule, applies it to the integrand, and reports the integral estimate.

The program can be invoked by a function call, in which case the string specifying f(x) must be quoted:

q = quad_trapezoid ( 'x^2', -1, 3, 5 )or, if called with no arguments, it will request them:

q = quad_trapezoid ( ) Enter function formula, like x^2: x^2 Enter left limit, a: -1 Enter right limit, b: 3 Enter number of interals: 5

The function is specified as a string which is either:

- a MATLAB expression using the argument 'x';
- the name of an M-file followed by the argument '(x)'.

The string should not contain any spaces between symbols, except when it is passed as a function argument in quotes.

It is not necessary to use the "dot" notation for expressions involving '*', '/', or '^', but it doesn't hurt either.

Examples of function specifications:

x^2 x.^2 3/(x^4+5*x-6) sin(7*x)*sqrt(x)/8 wiggle(x) <-- where "wiggle.m" is a user-provided M file.

The computer code and data files made available on this web page are distributed under the GNU LGPL license.

**quad_trapezoid** is available in
a MATLAB version.

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- quad_trapezoid.m the source code.