IXSMOOTH-Smooth in X-direction by gaussian convolution

Description:

IXSMOOTH smooths cross-sections of an array in the X-direction by convolving them with a gaussian of specified sigma and a specified cutoff width. Note that this is not a 2-D smooth, but a series of 1-D smooths; hence the name.

The VARIANCE array, if present, is propagated in exactly the same way as the DATA array. This procedure it not formally correct and the computed variance will probably under-estimate the true error.

Parameters:

IMAGE

Name of data to be smoothed.

SIGMA

Gaussian half width in pixels.

WIDTH

Pixels over which gaussian is calculated.

OUTPUT

Name of resulting data.

See also:

FIGARO: ICONV3, ISMOOTH, MEDFILT.
KAPPA: CONVOLVE, FFCLEAN, GAUSMOOTH, MEDIAN.

Source comments:

 I X S M O O T H

 This routine is the main body of IXSMOOTH, which smooths
 cross-sections of an array in the X-direction by convolving
 them with a gaussian of specified sigma and a specified
 cutoff width.  Note that this is not a 2-D smooth, but a series
 of 1-D smooths; hence the name.

 The VARIANCE array, if present, is propagated in exactly the same
 way as the DATA array.  This procedure it not formally correct and
 the computed variance will probably under-estimate the true error.

 Command parameters -

 IMAGE  The name of the structure containing the image.

 SIGMA  (Numeric) The sigma of the gaussian, expressed in array
        elements.  (This is approximately the half width at
        half maximum, to within a factor of ~1.17).

 WIDTH  (Numeric) The number of array elements over which the
        gaussian is calcualted - i.e. outside this range the
        gaussian is assumed to be zero.  This simplifies the
        computation and also allows the use of strangely shaped
        functions such as gaussians with very large sigmas but
        small widths - which are almost the same as rectangular
        filters.

 OUTPUT The name of the result of the operation.  This can
        be the same as for IMAGE.  If not, a new structure
        is created, with everything but the data a direct
        copy of the input.

                                  KS / CIT 23rd March 1983