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regionstats
June 28, 2006
Abstract
Compute statistics for an arbitrary region in an image.
1 Instruments/Modes
Not applicable. The task operates on any image.
Instrument Mode
2 Use
pipeline processing no
interactive analysis yes
3 Description
This task evaluates a number of statistics for a given region of interest. These are:
 centroid position
 position and value of maximum and minimum
 mean and standard deviation
 total number of counts
 number of pixels and number of bad pixels in the region
The corresponding statistical uncertainties are given as well.
The region is given in input as an saoimage compatible region le. If this le is not specied, the whole
image is used.
The user can optionally specify a quality data set to be used to mask the region of interest.
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Output positions are expressed in pixels and in WCS coordinates, if the appropriate information is
present.
Some of the functionality of this task is duplicated in eregionanalyse which may be more appropriate
for some scientic applications.
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
image yes string
name of the data set containing the image
usebadpix no bool no
Whether to use bad pixels.
badpix no string
Name of le containing bad pixels
useweight no bool no
Whether to use weights
weight no string
Name of le containing weights
xlowleft no 0 integer
X coord of lower left point of image
ylowleft no 0 integer
Y coord of lower left point of image
xupperright no 10 integer
X coord of upper right point of image
yupperright no 10 integer
Y coord of upper right point of image
events no events.ds:events string
Name of events le
agcolumn no FLAG string
Name of ag column in event le
xposcolumn no RAWX string
Name of rawx column in event le
yposcolumn no RAWY string
Name of rawy column in event le
countscolumn no COUNTS string
Name of countscolumn in event le
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weightcolumn no WEIGHT string
Name of weightcolumn in event le
probabilitycolumn no PROB string
Name of probability in event le
lter no no bool
Whether to lter le with an expression
lterexpression no no string
Expression with which to lter events
lter agcolumn no FILTERFLAG string
Name of lter column
statisticsset no statistics.ds string
Name of output le
5 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
6 Input Files
1. Any data set containing an image and, optionally, a quality and error arrays. Quality and
error data can also be stored in separate data sets.
2. Saoimage region denition le.
7 Output Files
None.
8 Algorithm
subroutine regionstats
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end subroutine regionstats
9 Comments
 The centroid will be meaningless if the region does not contain a point like source.
 The format and name of the quality and error data have not been agreed yet.
 The region selection should be carried out by rst unfurling the image in a pseudo event list,
then making a call to evselect (there will be an f90-callable interface), then computing the
relevant statistics on the ltered pseudo event list.
10 Future developments
References
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