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: http://xmm.vilspa.esa.es/sas/8.0.0/doc/colsmooth/node4.html
Дата изменения: Wed Jul 2 06:03:15 2008 Дата индексирования: Fri Sep 5 20:51:31 2008 Кодировка: Поисковые слова: п п п п п п п п п п п п п п п п п п п п п п п п |
The task convolves a specified column of a fits file by a user-specified convolving function. This can be used to smooth the values in the column. Specifically, for input vector defined from
to
and convolver
defined from
to
, colsmooth
performs the following transformation:
where
and the weight term is given by
These formulae automatically normalise the convolver . If this is not desired (indicated by setting the parameter normalise to `no'), the
values are multiplied by
in addition to the above.
The user may also specify an uncertainty column. The values of this column, which we denote by , are transformed as follows:
The vector here represents the transformed uncertainty values. The quantity
is given by
and is as given above. The
values can be `unnormalised' in the same way as
above.
It is probably as well to remind users that the benefits of smoothing are almost entirely cosmetic. The fundamental amount of information in the column cannot of course be increased by such processing. In fact use of a low-pass filter may be deceptive: the amount of noise may not have decreased very much although the graph looks much better because of the suppression of the more visible high-frequency end of the noise spectrum.
This task is not XMM-specific.
XMM-Newton SOC/SSC -- 2008-07-02