./guide
fshift.pro

Last modification date:

Thu Jun 2 23:56:08 2005

fshift

function fshift(accumnum, [index=integer], [frame=string])

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

You can use an alternate data container by setting index. You can use an alternate global accumulation buffer by setting accumnum.

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

Returns

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

Examples

 getps,30
 accum             ; accum first spectrum, no alignment needed yet
 getps,31
 fs = fshift()     ; determine the shift to align scan 31 with scan 30
 gshift,fs         ; spply the shift to scan 31
 accum             ; and add the result to the accumulator
 getps, 32
 gshift, fshift()  ; all in one line, shift scan 32 to align with scan 30
 accum
 ave
 

Uses

dcfshift

Version

$Id: fshift.pro,v 1.5 2005/06/02 17:09:44 bgarwood Exp $

Parameters
accumnum in integer (def. 0)	accum buffer to use. Defaults to the primary buffer, 0. There are 4 buffers total so this value must be between 0 and 3, inclusive.

Keywords
index in, optional integer (def. 0)	The data container that will eventually be shifted. Defaults to the primary data container (0).
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.