Averaging in split

Highlights on averaging using split

Time and channel averaging are available within split using the timebin and width parameters. The way that time averaging operates can be further controlled by combine, which is a sub-parameter of timebin.

The timebin parameter gives the averaging interval. It takes a quantity, e.g. timebin='30s' for 30-second time averaging.  By default the time-span of time averaging will be limited by scan boundaries, i.e. the time average will not be extended to average data from multiple scans together. Similarly, time averaging will by default not extend across state boundaries (states are telescope-specific entities; for ALMA a state corresponds to a sub-scan).  These default limits on time averaging can be modified by setting combine to 'scan', 'state', or 'state,scan' to ignore one or both types of boundaries and average across them.  combine is a sub-parameter of timebin which is enabled by selecting a non-zero time averaging interval.

The width parameter defines the number of channels to average to form a given output channel. This can be specified globally for all spw, e.g.

width = 5

or specified per spw, e.g.

width = [2,3]

to average 2 channels of 1st spectral window selected and 3 in the second one.

ALERT: When averaging channels split will produce negative channel widths (as reported by listobs) if frequency goes down with increasing channel number, whether or not the input channel widths are negative. The bandwidths and channel resolutions will still be positive."