./guide
gmeasure.pro

Last modification date:

Wed Sep 28 13:27:09 2016

gmeasure

procedure gmeasure, mode, fract, [brange=integer], [erange=integer], [rms=float], [/chan], [lefthorn=float], [righthorn=float], [/quiet], [ret=variable]

Procedure to measure the area, width, and velocity of a galaxy profile.

The derived area, width and velocity are displayed unless the /quiet keyword is used. These values can also be returned using the ret keyword. The value of ret is a 6-element array containing the area, width, and velocity in that order estimates of the error on those quantities in the same order. The width and velocity are always given (shown and returned) in km/s and the area is given in data units * km/s. The error on the area is only set when fract equals 0.2 or 0.5. The errors on the width and velocity are only set for mode 4. Mode 4 always sets the width error to be twice the velocity error.

This is a front-end to awv. The source code there originated at Arecibo. See the comments there for a description of the 4 possibly values for mode and how fract and rms are used for each mode.

The data that is currently displayed in the plotter is used in this procedure. The displayed x-axis can be any type. The x-axis values are be converted to velocity taking into account any previously set velocity offset (even if the displayed axis is not the velocity axis). If there is no data displayed in the plotter, the contents of the primary data container (buffer 0) are used.

If the region of interest is not specified, the user is asked to mark it interactively.

A baseline should have been removed prior to using this function.

brange, erange, lefthorn, and righthorn are given in the currently display x-axis units unless the chan keyword is set.

Originally Contributed By: Karen O'Neil, NRAO-GB and Bob Garwood, NRAO-CV

Examples

   gmeasure, 1, 0.5, ret=ret50
   gmeasure, 1, 0.8, ret=ret80
 

Uses

awv

Version

$Id$

Parameters
mode in, required integer	Must be one of 1,2,3, or 4. See the comments in awv for more details.
fract in, required float	Fraction of peak or mean used in locating the edges of the galaxy profile. See the comments in awv for more details. Note that in modes 3 and 4 the user is asked to mark the two horns of the galaxy profile with the cursor unless the optional lefthorn and righthorn keywords are used.

Keywords
brange in, optional integer	Starting value of the region of interest in x-axis units unless chan is set.
erange in, optional integer	Ending value of the region of interest in x-axis units unless chan is set.
rms in, optional float	Used in modes 2, 3 and 4 as described in . If this is not supplied, it defaults to the stddev of the data within the region of interest given by brange and erange.
chan in, optional boolean	Interpret the user supplied range and optional horn positions in channels instead of the current x-axis units.
lefthorn in, optional float	Location of the left peak in x-axis units unless chan was specified.
righthorn in, optional float	Location of the right peak in x-axis units unless chan was specified.
quiet in, optional boolean	When set, the results are not printed to the terminal (the ret keyword should be used to get the results).
ret out, optional variable	Six-element array giving [area,width,velocity,areaerr,widtherr,velocityerr]. All six elements will be 0.0 if there was a problem. The areaerr is only set when fract is 0.2 or 0.5. The widtherr and velocityerr are only set by mode 4. Unset error values are 0.0.