# getmin: Approximates the minimum of a function given on a grid In DeconWK: Deconvolution by Weighted Kernels

## Description

Approximates the minimum of a function given on a grid. Quadratic approximation around the point where the mimimal function value is observed is used (if that point is in the interior).

## Usage

 `1` ```getmin(x, y, which="global", count.minima=FALSE, verbose=TRUE) ```

## Arguments

 `x` Vector with the x-values at which the function is observed. Should be sorted. `y` Vector with the function values. `which` Defines which miminum we want to find. Possible values are "global" for the global minimum, "left" for the left-most local minimum and "right" for the right-most local minimum. Abbreviations ("g", "r", "gl", etc.) may be used. `count.minima` If TRUE, the number of local minima in the observed function values is returned. `verbose` If TRUE, the routine will give a warning if any exceptions occur.

## Value

A list with the following elements is returned:

 `xmin` The x-coordinate of the minimum. `ymin` The approximate value of the function at the minimum. `nmin` The number of local minima in the y-vector (if requested, otherwise 0). `excep` Indicates whether an exeption has occurred: -1 if the minimum was found at the left end, 1 if the minimum was found at the right end, 5 if the minimum was in the middle but the quadratic fit yielded a location of the minimum which was outside of the interval defined by the three points used for the quadratic fit and 0 in all other cases.

## Note

The vector x must be sorted.

## Author(s)

Berwin A Turlach [email protected]

## Examples

 ```1 2 3``` ``` x <- -100:100/50 y <- x*x getmin(x,y) ```

DeconWK documentation built on May 31, 2017, 4:32 a.m.