Keywords: class

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## Entry Number and Index

The `FIND` command offers the possibility to build an index of the observations matching several given selection criteria. The user can then easily process consistently only those observations. Each time a new index is formed using the `FIND` command, all the selected observations (which will belong to this index) are sequentially attributed a number, named entry number. This number goes from 1 to `found`, the number of observations in the current index. The entry number is never saved. It is just used as a number to process the current index in a loop.

Default selection criteria are defined by the `SET` command. For most selection criteria, an option to the `FIND` command exists, with the same name, which may be used to impose temporary values to the `FIND` command; the default values are unchanged by the `FIND` options.

- `SET LINE` `Name` for the line name to be used. A line name of the form `ABC*` indicates that all lines beginning by `ABC` are to be selected. The default is `*`, i.e. any line name.
- `SET NUMBER` `n1 n2` for the range of observation numbers. Default is `* *`, i.e. any observation number; `* n2` specifies all observation numbers smaller than n2.
- `SET OBSERVED` `d1 d2` for the range of observing dates. A date is specified in the format `dd-mmm-yyyy`, e.g. 19-jan-1985. Default is `* *`, i.e. any date; `19-JAN-1985 *` means any date later than January 19th, 1985.
- `SET OFFSET` `o1 o2` for offsets of the position to be used (in the system and units specified by `SET COORDINATE` and `SET ANGLE`). Default is `* *`.
- `SET RANGE` `w e s n` is a less restrictive way to specify position offsets. A rectangular area of sky is defined by its west, east, south and north limits (in current angle units).
- `SET REDUCED` `d1 d2` for a range in reduction dates; same specifications and defaults as for `SET OBSERVED`.
- `SET SOURCE` `Name` for the source name; same specifications as `SET LINE`.
- `SET SCAN` `s1 s2` for a range of original scan numbers. Scan numbers should not be confused with Observation numbers (the numbers by which an observation is uniquely identified). They are essentially ``history'' numbers defined by the acquisition system, but usually with different ``observations'' (in the CLASS meaning) for a single scan. The scan number is kept only for bookkeeping purpose.
- `SET TELESCOPE` `Name` for the Telescope name. For the IRAM 30-m telescope, the telescope name contains coded into the last 3 letters the backend used for the observations. Similar conventions are used for spectra coming from Plateau de Bure Interferometer.
- `SET TYPE` `Name` specifies on which type of observations you deal with: ``Continuum'', ``Line'' or ``Skydip''.

The tolerance parameter defined by `SET MATCH` also influences on the position searches, since this parameter (in the current angle unit) is used to check agreement with the specified limits. Another option to the `FIND` command is `/ALL` which enables to find all the versions of all observations satisfying the selection criteria (otherwise only the most recent version is selected). Note that the system is intended to work only with the last version of observations, so that the use of the `/ALL` option should remain exceptional.

Finally, the `SET SORT` force the `FIND` command to sort all the entries of an index in ascending order of a key parameter (e.g. lambda or beta offsets). `SET SORT number` implies the default order.

Next: R and T Memories Up: Generalities Previous: Scan and Subscan Number Contents Index