ms.range - Function

Get the range of values in the measurement set

Synopsis
range(items, useflags, blocksize)

Arguments

items	in	Item names
		Allowed:	Vector of strings
		Default:	no default
useflags	in	Use the data flags
		Allowed:	Bool
		Default:	T
blocksize	in	Set the blocksize in MB
		Allowed:	Int
		Default:	10

Returns
record with ranges for the requested items

Description
This function will return the range of values in the currently selected measurement set for the items specified. Possible items include most scalar columns, interferometer number (1000*antenna1+antenna2), uvdist(ance), u, v, w, amplitude, phase, real and imaginary components of the data (and corrected and model versions of these - if these columns are present). See the table at the top of the document to find the exact list.

You specify which items you are interested in using a string vector where each element is a case insensitive item name. This function will then return a record that has fields corresponding to each of the specified items. Each field will contain the range of the specified item. For many items the range will be the minimum and maximum values but for some it will be a list of unique values. Unrecognized items are ignored. By default the FLAG column is used to exclude flagged data from before any ranges are determined, but you can set useflags=F to include flagged data in the range (but if you average in frequency, flagging will still be applied).

You can influence the memory use and the reading speed using the blocksize argument - it specifies how big a block of data to read at once (in MB). For large datasets on machines with lots of memory you may speed things up by setting this higher than the default (10 MB).

For some items, as indicated with an § in table 1.355 (in the general description of this tool), you need to call selectinit to select a portion of the data with a unique shape prior to calling this function.

Items prefixed with either; corrected, model, residual or obs_residual and the imaging_weight item are not available unless your measurement set has been processed either with the imager or calibrator tools.

Example

      include 'ms.g'
      myms:=ms("3C273XC1.ms");
      myms.selectinit(datadsescid=1);
      a.range("time uvdist amplitude antenna1")
      [time=[4.12163e+09 4.12164e+09] ,
       uvdist=[46.2691 3727.97] ,
       amplitude=[0.0260339 33.8518] ,
       antenna1=[1 2 3 4 ... 27] ]

In this example the minimum and maximum observation times, uvdistances, data amplitudes are returned as well as a list of all the antennas in the antenna1 column. Note that the double quoted string produces a string vector as the input argument.

For this dataset the selectinit function did not need to be called as all the data is of one shape.

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	Package	general
	Module	ms
	Tool	ms