FINDMAX

Name

findmax

Purpose (one Line)

Find the interpolated local maximum in a 2-D array.

Description

Calling Sequence

findmax, x, y, f, xmax, ymax, fmax, $
DELTA=in_delta, EPS=in_eps, GOLD=in_gold

Inputs

x, y : Position of the initial guess.
f : The 2-D function array.

Optional Input Parameters

Keyword Parameters

DELTA = Half-width of the box containing the desired maximum.
Default is 1.0 pixel.
EPS = Stop criterion. Default=1.0E-5.
GOLD = Pad value on DELTA. Default is 1.0E-4.

Outputs

xmax, ymax : Position of computed maximum.
fmax : Computed function maximum.

Common Blocks

Side Effects

Restrictions

Procedure

Binary search (2D).
A guess for the location of the maximum is chosen. The external function
sint2d is called to obtain interpolated function values at two symmetric
points along each axis (x and y). For each axis, the two points are used
to determine which way to shift the location of the maximum. IF the
function values at the two points are not equal, the location of the
maximum is shifted by half the previous amount in the indicated direction,
and a new set of four points are computed at half the offset used previously.
This process continues until the offset falls below some small threshold
value (epsilon).

Modification History

Written by Doug Loucks, Lowell Observatory, September, 1993.
2007/06/21, MWB, promote x,y inputs to float (internally only).