nonlin_bisect, an Octave code which interactively applies bisection to seek a root of f(x) over a change-of-sign interval a <= x <= b.
The user enters a formula for f(x), and the values of a and b. It must be the case that the signs of f(a) and f(b) are opposite.
The program then repeatedly applies bisection until the width of the interval is very small.
The program can be invoked by a function call, in which case the string specifying f(x) must be quoted:
[ a, b, fa, fb ] = nonlin_bisect ( 'x^2-4', -1, 3 )
or, if called with no arguments, it will request them:
[ a, b, fa, fb ] = nonlin_bisect ( );
Enter function formula, like x^2-4: x^2-4
Enter left limit, a: -1
Enter right limit, b: 3
The function is specified as a string which is either:
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 information on this web page is distributed under the MIT license.
nonlin_bisect is available in a MATLAB version and an Octave version.
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