Flags

Each record contains one flag word by antenna, and one flag word by baseline. There may ultimately 32 flags in each word. As for now, both antenna and baseline flag words may contain one flag by subband (named CO1 to C06, and L01 to L06; in addition, the antenna flag words may contain flags LOCK, TSYS, POINTING, SHADOW, and DATA, while the baseline flagwords may contain flag DATA.

For instance, if subband flag C02 is present in baseline 23, subband C02 will be ignored for further processing of baseline 23 (in particular, it will be absent from plots). If present in antenna 1, baselines 12 and 13 will be affected. Other flags such as LOCK, TSYS, POINTING, SHADOW, and DATA will affect all subbands of the relevant baselines. Flags should normally be set by the real time system, or the real time calibration step in CLIC.

You may wish to use that data anyway, by masking them (command MASK). For instance use MASK C02 /BASELINE 23 if you feel that this subband was usable, but do not be surprised by the results !

You may also want to suppress temporarily some data channels from plots or from output tables, without modifying the data file itself. This is done by command MARK. Marked data channels will be ignored just as if they were flagged in the data.

On the opposite, you might have to flag some data yourself. There are several ways of doing this:

• using the command STORE FLAG which will flag all the records of all the scans in the current index. For instance

  FIND /SCAN 5436
  STORE FLAG DATA /BASELINE 12
  

  will flag baseline 12 for the whole duration of scan 5436. This is the best way to flag one or more complete scans.
• using command MODIFY DATA, with a procedure DATA.CLIC containing the command FLAG. For instance, assume that you want to discard all data where the total power on antenna 2 is lower than some threshold, say 10. You will create a procedure DATA.CLIC:

  IF DH_TOTAL[2].LT.10. THEN
      FLAG DATA /ANTENNA  2 
      GO WRITE
  ELSE
      GO
  ENDIF
  

  Do not forget to enable variables of group DATA_HEADER, before typing MODIFY DATA.
• interactively, after a GET /RECORD, use the FLAG command to set or reset a flag for this specific record. The UPDATE command will write back the flagged data to the file.
• interactively, with command CURSOR. Assume you have plotted amplitude versus time (with no averaging), you should have one point for each record. Then you can select a range of records in X coordinate: point the cursor to the first point you want to flag, type N (for New range), then go to the last point, type F (for Flag). You will be prompted for the name of the flag to set. This flag will be set for the baseline, or antenna, corresponding to the box you are pointing to with the cursor.

You may get a status of the flags in the data og the current index by issuing command LIST /FLAG.