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moment

Section: User Commands (1)
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NAME

moment - Calculate moments of a Miriad image.  

PERSON RESPONSIBLE

mchw  

CATEGORIES

image analysis  

DESCRIPTION

MOMENT calculates the nth moment of a Miriad image. Currently only the moment of axis 1 or axis 3 is calculated for 3 dimensional images. To obtain the moments for other axes use the task REORDER to reorder the axes. Although by default MOMENT has a somewhat user centric notion of the moment= keyword, raw moments can be computed in raw mode.  

PARAMETERS

in
The input image. No default.
region
The region of the input image to be used. See documentation for region on how to specify this. Only the bounding box is supported.
out
The output image. No default.
mom
-3 Velocity at peak, using a 3 point polynomial fit around the peak -2 Peak temperature (units are same as individual channels) -1 Average intensity. (units are same as individual channels)
 0      Integrated intensity. (e.g. units I x km/s)
 1      1st moment = sum(I*v)/sum(I)
 2      dispersion = sqrt(sum(I*(v-M1)**2)/sum(I))
        The v(i) are the axis values (e.g. velocities).  M1 is the first
        moment. The moment is calculated independently for each pixel
        within the specified clip range. Default = 0.
        Note that mom=2 produces a map of sigma ('gaussian' dispersions), 
        with FWHM = 2*sqrt(2*ln(2)) = 2.355  * sigma if the profile was
        a true gaussian.
axis
The axis for which the moment is calculated. Default = 3.
clip
Two values. Exclude pixels with values in the range clip(1) to clip(2). If only one value is given, then exclude -abs(clip) to abs(clip).
rngmsk
Mask pixels as bad when the 1st moment gives a 1st moment out of range of that of the axis. This option can only be activated for mom=1. Default: false
raw
By default, moment is user oriented, i.e. mom=1 computes the velocity. By setting raw=true, you will get the raw sum(I*v**mom) and will have to use MATHS to compute back the various maps. Currently only supported for axis=3. If the velocity scale is very large and/or mom is large, a rescale using PUTHD on crval3/cdelt3 may be needed. Default: false


 

Index

NAME
PERSON RESPONSIBLE
CATEGORIES
DESCRIPTION
PARAMETERS

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Time: 18:35:38 GMT, July 05, 2011