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Last modified: December 2009

URL: http://cxc-newtest.cfa.harvard.edu/ciao4.2/grpbinwidth.html
AHELP for CIAO 4.2

grpBinWidth

Context: group

Synopsis

Group an array into a set of equal-width groups (by group width).

Syntax

grpBinWidth( Integer_Type numChans, Integer_Type grpWidth )
grpBinWidth( Integer_Type numChans, Integer_Type grpWidth, Array_Type
tabStops )

Returns: ( Array_Type grouping, Array_Type quality )

Description

This function returns the grouping and quality arrays that represent an array of numChans elements in which the groups are each grpWidth elements wide. The optional parameter tabStops is an array which lists those elements that should be ignored. The tabStops array must be the same length as the channels array. A value of 0 means no tab; a value of 1 means that there is a tab stop.

This function provides the same functionality as the BIN_WIDTH option of dmgroup. The grpNumBins() function allows you to fix the number of groups rather than the width of each group.

The group module is not available by default; to use it in a S-Lang program, it must be loaded using the S-Lang require() function:

  require("group");

Example 1

slsh> (g,q) = grpBinwidth( 10, 2 );

This example calculates the grouping and quality arrays that represent an array of 10 elements in which each group has a width of 2 elements.

Example 2

slsh> x = [0.5:6.0:0.05];
slsh> y = 3 + 30 * exp( - (x-2.0)^2 / 0.1 );
slsh> (g,q) = grpBinWidth( length(y), 10 );
slsh> ysum = grpGetGroupSum( y, g );
slsh> nchan = grpGetChansPerGroup( g );
slsh> i = where( g == 1 );
slsh> yavg = ysum[i] / nchan[i];

Here we take the function

y = 3 + 30 * exp( -(x-2)^2 / 0.1 )

and group it so that each group contains 10 elements.

If we had filtered the data array to only contain elements with a quality value - as returned by grpBinWidth() - of 0, then we could have avoided the call to grpGetChansPerGroup() since this is set to 10 by grpBinWidth().

Bugs

See the bugs page for the group library on the CIAO website for an up-to-date listing of known bugs.

See Also

group
grpadaptive, grpadaptivesnr, grpbin, grpbinfile, grpbinwidth, grpgetchanspergroup, grpgetgroupsum, grpgetgrpnum, grpmaxslope, grpminslope, grpnumbins, grpnumcounts, grpsnr
modules
group_slang

Last modified: December 2009