NAME:
	LocalExtrema
 PURPOSE:
	Return location of local maxima and minima in an array
 CATEGORY:
	Math
 CALLING SEQUENCE:
	R = LocalExtrema(Array, [/minima, /float])
 INPUTS:
	Array	    array[*]; type: 1-dim array
			input array to be searched for extrema
 OPTIONAL INPUT PARAMETERS:
	By default the locations of an alternating sequence of
	maxima and minima are returned.

	/maxima     if /maxima is set then the locations of maxima are returned
	/minima     if /minima is set then the locations of minima are returned

	/float	    by default integer indices are returned for the location of the extrema.
		    If /float is set then the location is refined by fitting a quadratic to
		    the minimum element and its two neighbours. The extremum of the
		    quadratic is returned as a floating point number.
 OUTPUTS:
	R	    scalar or array; type: integer or float
			indices of minima or maxima
 OPTIONAL OUTPUT PARAMETERS:
	fnc=fnc     array[*]; same size as R, same type as 'Array'
			function values in locations R. If the /float keyword is set it
			returns the function values in the extremum of the quadratic fit.
	count=count scalar; type: integer
			# extrema
 INCLUDE:
	@compile_opt.pro	    ; On error, return to caller
 CALLS: ***
	BadValue, InitVar
 CALLED BY:
	even_light_pedestal, smei_frm_hbar
 RESTRICTIONS:
 >	Only genuine maxima and minima are detected,
 >	The edges of the array are excluded, i.e. only the locations of
	'internal' extrema (with neighbour on both sides) are returned
 PROCEDURE:
	Let 'array' represent a function f(x) in points x=[0,1,.]
	Let f have an extremum in grid point j, i.e. f(j) > f(j-1) and f(j) > f(j+1)
	Define dx = x-j and g(dx) = f(j+dx)-f(j), i.e. g(0) = 0 is an extremum of g
	The quadratic for g through 0 and its two neighbours -1 and +1 is:
	    y(dx) = 0.5*dx*{ g(-1)*(dx-1)+g(+1)*(dx+1) }
	which has a maximum at
	    dx = 0.5*(g(-1)-g(1))/(g(-1)+g(1))
 MODIFICATION HISTORY:
	MAR-2000, Paul Hick (UCSD/CASS)
	FEB-2004, Paul Hick (UCSD/CASS; pphick@ucsd.edu)
	    Introduced /maxima keyword to return maxima. This used to be the default.
	    The default now is to return an alternating sequence of minima and maxima.