6.2 Printer displays of your data

The most old fashioned way to look at your data — and the most exact — is simply to print it out and read the numbers. AIPS provides a variety of tasks and verbs to print visibility data, image data, tabular data, and miscellaneous other information. All of these tasks and verbs allow you to specify where the printed output goes using two adverbs, DOCRT and OUTPRINT. If DOCRT0 and OUTPRINT is blank, then the output is placed in a temporary file and queued to the printer you selected when starting AIPS; see 2.2.3. Beginning with 31DEC16, if printing directly to the printer is requested, most tasks and verbs count the number of lines of print and request permission to proceed if the count is large. (Type PRINTER n  C R to change the line printer selection to that numbered n; type PRINTER 999  C R to see the devices available to you and their assigned numbers.) If DOCRT0, a non-blank OUTPRINT specifies a text file into which the output is to be written; see 3.10.1. The current output is appended to the file if it already exists. Thus, you can combine a number of printed outputs for later editing and/or printing. When DOCRT = -1, the output print file will contain full paging commands and headers. To suppress some of this, use DOCRT = -2 or to suppress almost all of it, use DOCRT = -3. This last is especially helpful when writing programs to read the text file. If DOCRT > 0, the output is directed to your workstation window or terminal. All printer verbs and tasks are able to respond to both the width and height of your workstation window. Set DOCRT = 1 to use the current width; set DOCRT = n 72, to use n as the width of the display window. Since most print tasks display more information on wider windows, we recommend widening your window to 132 characters and specifying DOCRT = 1. The print routines will pause whenever the screen is full and offer you the choice of continuing or quitting. Thus, you can start what might be a very long print job, find out what you wanted to know after a few screens full, and quit without using up any trees.

6.2.1 Printing your visibility data

Before beginning calibration, it is a very good idea to make a -summary list of the contents of your data set. LISTR with OPTYPE = ’SCANwill list the contents of each scan in the data set. DTSUM also produces a listing summarizing the data set in either a condensed or full form.

The most basic display of your visibility data is provided by PRTUV which lists selected correlators in the order they occur in the data set:

> TASK PRTUV’ ; INP  C R

to review the inputs.

> INDI n ; GETN ctn  C R

to select the disk and data set to print.

> CHANNEL c ; BIF 1  C R

to print starting with channel c from IF 1.

> BPRINT m; XINC i  C R

to print every ith visibility starting with the mth visibility in the data set.

> DOCRT 1 ; GO  C R

to run the task with display on the terminal.

When you have seen enough, enter q  C R or Q  C R at the page-full prompt.

You may limit the sources, range of projected baselines, and times displayed and may select only one baseline or one antenna. PRTUV does not apply calibration or flagging tables. To get a similar display with all “standard” calibration, flagging, and data selection (optionally) applied, use the task UVPRT. LISTR also uses all of the calibration options to list the data in simple lists or in a display showing all the baselines at each time in a matrix form. SHOUV also lists calibrated visibility data with options to average all channels in each IF and to display closure rather than observed phases. ANBPL converts baseline-based amplitudes, phases, or weights into antenna-based values and prints and/or plots them. The display of antenna-based weights before and after amplitude self-calibration is a particularly useful tool for spotting calibration/instrumental problems.

There are a number of tasks used to diagnose possible problems in your data and to print information about them. UVFND examines a data set for excess fluxes, excess apparent V-polarization, or simply any data with a specified fringe spacing and position angle or a specified range in u and v. As it does this, it also checks for bad antenna numbers, bad times, and (optionally) bad data weights. CORER examines a data set for excessive mean values and rms in each correlator (after applying calibration and flagging and then subtracting a point source at the origin). RFI examines the rms fluctuations in the real and imaginary visibilities of each correlator looking for (and reporting) periods of apparent RF interference. UVDIF directly compares two data sets reporting any excess differences. It is useful for determining whether your latest operations (flagging, self-cal) have made a significant (or any) difference.

6.2.2 Printing your image data

The most basic display of an image is a print out of the numbers it contains. Such a display is provided by PRTIM:

> TASK PRTIM’ ; INP  C R

to review the inputs.

> INDI n ; GETN ctn  C R

to select the disk and image to print.

> NDIG 3  C R

to use 3 digits, printing numbers between -99 and 999 with appropriate power of 10 scaling.

> FACTOR 10  C R

to raise the default scaling by a factor of 10, overflowing regions of high values to see low valued regions better.

> BLC 0 ; TRC 0  C R

to see the whole image.

> XINC 2 ; YINC 2  C R

to see every other column and every other row.

> DOCRT FALSE ; GO  C R

to print the image on the selected printer.

Other imaging tasks which can use the printer are BLSUM and ISPEC, which compute and print spectra by summing over regions of each plane in a data cube (see 8.6), and IMFIT, JMFIT, and SAD, which fit one or more Gaussians to an image (see 7.5). IMTXT writes an ASCII-formatted file containing an image.

6.2.3 Printing your table data

If you have any doubts about the contents of tables in AIPS, it is best to resolve them by looking at the contents of the tables involved. PRTAB is a very general task which will print the contents of any AIPS table file. For example, to print flag table version 1:

> TASK PRTAB’ ; INP  C R

to review the inputs.

> INDI n ; GETN ctn  C R

to select the disk and catalog entry to print.

> INEXT ’FG’ ; INVERS 1  C R

to select flag table version 1.

> BPRINT 0 ; EPRINT 0 ; XINC 1  C R

to print everything.

> DOHMS TRUE  C R

to print times in sexagesimal notation.

> DOCRT 1 ; GO

to print the flag table on the terminal.

When you have seen enough, enter q  C R or Q  C R at the page-full prompt. For a table with a significant number of columns, PRTAB shows all rows for the first columns and then loops for the next set of columns. To see all columns for some rows, set a low EPRINT value or be very patient. Enter a list of column numbers in BOX to see only some of the columns. NCOUNT, BDROP and EDROP control which values are displayed in those columns having more than 1 value per row. Adverb RPARM lets you limit the display to rows having specific column values within specified ranges, while NDIG controls the format and accuracy used to display floating-point columns.

Some of the tables have specialized printing programs. These include PRTAN for antenna tables, PRTCC for Clean component tables, SLPRT for slice files, and LISTR with OPTYPE = ’GAINfor calibration, solution, and system temperature tables. The verb EXTLIST will list information about various extension files, particularly slice and plot files (see below), which may be printed with PRTMSG. OFMLIST is a verb to print the contents of an AIPS TV color table. Finally, task TBDIF will compare columns of two tables and print information about their differences.

6.2.4 Printing miscellaneous information

There is a variety of miscellaneous information which may also be sent to the printer in the same way. Verb PRTMSG prints selected contents of the AIPS message file; see 3.2. Verb PRTHI prints selected lines from a history file; see 3.4. Pseudo-verb ABOUT prints lists of AIPS symbols by category while pseudo-verbs HELP and EXPLAIN print information about a selected symbol; see 3.8. Task PRTTP prints the contents of magnetic tape volumes and pseudo-tape disk files; see 5.1.1 and 3.9.4. Task PRTAC, which may also be run in a stand-alone mode, prints information selected from the AIPS accounting file.

Task TXPL will attempt to represent an AIPS plot file (see below) on the printer. This will not work well for complicated plots, but, for simple plots, it may be the only way someone running over a slow telephone line can see his/her data in plot form.