./toolbox
dcvshift.pro

Last modification date:

Wed Sep 28 13:27:10 2016

dcvshift

function dcvshift(accumbuf, dc, [frame=string], [veldef=string], [voffset=double])

Function to calculate the shift, in channels, necessary to align in velocity a data container with the data container template in an ongoing accumulation.

If the frame is not set, the one implied by the data header is used. Use dcxshift to align using the current settings of the plotter's x-axis.

Returns

shift, in channels, to be used as argument to dcshift. Returns 0.0 on error.

Examples

 a={accum_struct}
 getps,30
 dcaccum, a, !g.s[0]  ; start an accum, no alignment needed yet
 getps,31
 vs = dcvshift(a,!g.s[0]) ; what is the shift to align 31 with 30?
 ; get a copy of data at !g.s[0]
 data_copy,!g.s[0], d
 dcshift, d, vs  ; actually shift the data
 dcaccum, a, d ; and add it in
 getps, 32
 data_copy,!g.s[0], d
 dcshift, d, dcvshift(a, d)  ; all in one line, shift 32 to align with 30
 dcaccum, a, d
 accumave, a, d ; result is in d now
 

Version

$Id$

Parameters
accumbuf in, required accum_struct	The ongoing accumulation buffer.
dc in, required spectrum	The data container that needs to be shifted to align with the data container template in accumbuf.

Keywords
frame in, optional string	The reference frame to use. If not supplied, the value implied by the last 4 characters of the velocity_definition in the ongoing accumulation will be used. See frame_velocity for a full list of supported reference frames.
veldef in, optional string	The velocity definition to use. If not supplied, the value implied by the first 4 characters of the velocity_definition in the ongoing accumulation will be used. See frame_velocity for a full list of supported reference frames.
voffset in, optional double	A velocity offset in km/s to apply before aligning. If not set, this defaults to a value of 0.0. A typical use would be to set this equal to the source velocity (at the velocity header value). Not that the units expected here are km/s, in agreement with those expected for setvoffset. The units for the velocity header field are m/s.