Re: [Help-gsl] Getting the index of a sorted vector entry closest to a certain value

[Brian Gough]

At Tue, 8 Jun 2010 13:31:29 -0700,
Luke wrote:
> 
> I have a gsl_vector whose values are evenly space from -M_PI to M_PI.
> I am using the GSL single dimensional root finding algorithm on a
> single equation which gives me a value that is in the range of [-M_PI,
> M_PI], but won't be exactly equal to any of the elements.  My goal is
> to find the index of the element in my gsl_vector which is closest to
> the solution from the root finding algorithm.  Here is an illustration
> of situation:
> 
> v = {-1.0, -0.5, 0.0, 0.5, 1.0}
> x_star = 0.3
> 
> Since the entry of v closest to x_star is 0.5, the index I would want
> to obtain is i = 3.
> 
> I would imagine the function call to be something like:
> 
> i = get_nearest_index(v, x_star);

Hi

See the Interpolation chapter of the manual in the section on "Index
Look-up and Acceleration"

-- 
Brian Gough