funcen(1)							SAORD Documentation							 funcen(1)

NAME

       funcen - find centroid (for binary tables)

SYNOPSIS

       funcen [-i] [-n iter] [-t tol] [-v lev] <iname> <region>

OPTIONS

	 -i	       # use image filtering (default: event filtering)
	 -n iter       # max number of iterations (default: 0)
	 -t tol        # pixel tolerance distance (default: 1.0)
	 -v [0,1,2,3]  # output verbosity level (default: 0)

DESCRIPTION

       funcen iteratively calculates the centroid position within one or more regions of a Funtools table (FITS binary table or raw event file).
       Starting with an input table, an initial region specification, and an iteration count, the program calculates the average x and y position
       within the region and then uses this new position as the region center for the next iteration. Iteration terminates when the maximum number
       of iterations is reached or when the input tolerance distance is met for that region. A count of events in the final region is then output,
       along with the pixel position value (and, where available, WCS position).

       The first argument to the program specifies the Funtools table file to process.	Since the file must be read repeatedly, a value of "stdin"
       is not permitted when the number of iterations is non-zero.  Use Funtools Bracket Notation to specify FITS extensions and filters.

       The second required argument is the initial region descriptor. Multiple regions are permitted. However, compound regions (accelerators,
       variable argument regions and regions connected via boolean algebra) are not permitted. Points and polygons also are illegal. These
       restrictions might be lifted in a future version, if warranted.

       The -n (iteration number) switch specifies the maximum number of iterations to perform. The default is 0, which means that the program
       will simply count and display the number of events in the initial region(s).  Note that when iterations is 0, the data can be input via
       stdin.

       The -t (tolerance) switch specifies a floating point tolerance value. If the distance between the current centroid position value and the
       last position values is less than this value, iteration terminates.  The default value is 1 pixel.

       The -v (verbosity) switch specifies the verbosity level of the output. The default is 0, which results in a single line of output for each
       input region consisting of the following values:

	 counts x y [ra dec coordsys]

       The last 3 WCS values are output if WCS information is available in the data file header. Thus, for example:

	 [sh] funcen -n 0 snr.ev "cir 505 508 5"
	 915 505.00 508.00 345.284038 58.870920 j2000

	 [sh] funcen -n 3 snr.ev "cir 505 508 5"
	 1120 504.43 509.65 345.286480 58.874587 j2000

       The first example simply counts the number of events in the initial region.  The second example iterates the centroid calculation three
       times to determine a final "best" position.

       Higher levels of verbosity obviously imply more verbose output. At level 1, the output essentially contains the same information as level
       0, but with keyword formatting:

	 [sh] funcen -v 1 -n 3 snr.ev "cir 505 508 5"
	 event_file:	 snr.ev
	 initial_region: cir 505 508 5
	 tolerance:	 1.0000
	 iterations:	 1

	 events:	 1120
	 x,y(physical):  504.43 509.65
	 ra,dec(j2000):  345.286480 58.874587
	 final_region1:  cir 504.43 509.65 5

       Level 2 outputs results from intermediate calculations as well.

       Ordinarily, region filtering is performed using analytic (event) filtering, i.e. that same style of filtering as is performed by fundisp
       and funtable. Use the -i switch to specify image filtering, i.e. the same style filtering as is performed by funcnts.  Thus, you can per-
       form a quick calculation of counts in regions, using either the analytic or image filtering method, by specifying the
	-n 0 and optional -i switches. These two method often give different results because of how boundary events are processed:

	 [sh] funcen  snr.ev "cir 505 508 5"
	 915 505.00 508.00 345.284038 58.870920 j2000

	 [sh] funcen -i snr.ev "cir 505 508 5"
	 798 505.00 508.00 345.284038 58.870920 j2000

       See Region Boundaries for more information about how boundaries are calculated using these two methods.

SEE ALSO

       See funtools(7) for a list of Funtools help pages

version 1.4.2							  January 2, 2008							 funcen(1)