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| <pre>
| | {{immoments}} |
| Help on immoments task:
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| Compute moments from an image
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| The spectral moment distributions at each pixel are
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| determined. See the cookbook and User Reference Manual for
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| mathematical details.
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| The main control of the calculation is given by parameter
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| moments:
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|
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| moments=-1 - mean value of the spectrum
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| moments=0 - integrated value of the spectrum
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| moments=1 - intensity weighted coordinate;traditionally used to get
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| 'velocity fields'
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| moments=2 - intensity weighted dispersion of the coordinate; traditionally
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| used to get "velocity dispersion"
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| moments=3 - median of I
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| moments=4 - median coordinate
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| moments=5 - standard deviation about the mean of the spectrum
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| moments=6 - root mean square of the spectrum
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| moments=7 - absolute mean deviation of the spectrum
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| moments=8 - maximum value of the spectrum
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| moments=9 - coordinate of the maximum value of the spectrum
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| moments=10 - minimum value of the spectrum
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| moments=11 - coordinate of the minimum value of the spectrum
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| Keyword arguments:
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| imagename -- Name of input image
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| default: none; example: imagename="ngc5921_task.image"
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| moments -- List of moments you would like to compute
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| default: 0 (integrated spectrum);example: moments=[0,1]
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| see list above
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| axis -- The moment axis
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| default: (spectral axis); example: axis=spec
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| options: ra, dec, lattitude, longitude, spectral, stokes
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| mask -- Mask applied to the image before calculating the moments.
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| Default "" means no mask;
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| Example: mask="orion.mask".
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| Full description of the syntax can be found at
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| http://www.astron.nl/aips++/docs/notes/223/node11.html>Aips++ Notes series
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| region -- File path to an ImageRegion file or the name of
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| a region stored within the image..
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| Default: none;
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| Example: region="myimage.im.rgn"
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| region="region1"
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| box -- A box region on the directional plane
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| Only pixel values acceptable at this time.
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| Default: none;
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| Example: region="myimage.im.rgn"
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| region="region1"
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| box -- A box region on the directional plane
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| Only pixel values acceptable at this time.
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| Default: none (whole 2-D plane);
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| Example: box="10,10,50,50"
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| box = "10,10,30,30,35,35,50,50" (two boxes)
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| chans -- channel numbers
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| Range of channel numbers to include in statistics
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| All spectral windows are included
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| Default:""= all; Example: chans="3~20"
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| stokes -- Stokes parameters to analyze.
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| Default: none (all); Example: stokes="IQUV";
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| Example:stokes="I,Q"
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| Options: "I","Q","U","V","RR","RL","LR","LL","XX","YX","XY","YY", ...
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| includepix -- Range of pixel values to include
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| default: [-1] (all pixels); example=[0.02,100.0]
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| excludepix -- Range of pixel values to exclude
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| default: [-1] (don"t exclude pixels); example=[100.,200.]
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| outfile -- Output image file name (or root for multiple moments)
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| default: "" (input+auto-determined suffix);example: outfile="source_moment"
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| Example for finding the 1-momment, intensity-weighted
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| coordinate, often used for finding velocity fields.
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| immoments( axis="spec", imagename="myimage", moment=1, outfile="velocityfields" )
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| Example finding the spectral mean, -1 moment, on a specified region
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| of the image as defined by the box and stokes parameters
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| taskname="immoments"
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| default()
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| imagename = "myimage"
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| moment = -1
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| axis = "spec"
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| stoke = "I"
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| box = [55,12,97,32]
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| go
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| Example using a mask created with a second file to select the
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| data used to calculate the 0-moments, integrated values. In
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| this case the mask is from the calibrated.im file and all values
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| that have a value greater than 0.5 will be positive in the mask..
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| immoments( "clean.image", axis="spec", mask="calibrated.im>0.5", outfile="mom_withmask.im" )
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| </pre>
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