VPLOT VPLOT is a program for interactive display and examination of visibility data files (MERGE files) and models. It is superior to VISPLOT for some purposes, but does not yet have all of VISPLOT's capabilities. Suggestions for improvements are welcome. VISPLOT has several shortcomings which are particularly noticeable when plotting datasets with short scans, many antennas, or scans spread over several days. First, it is very slow: this is because it was written in the days when memory was expensive. Each time you display a baseline, VISPLOT reads through the entire dataset to find the data for that baseline. Second, it is not very interactive: it was originally written for the batch-only, card-input IBM 370 at Caltech. Third: it has some bugs, such as omitting to plot the model when scans are very short. The bugs could be fixed, but only with great difficulty: the code is no longer transparent. Finally, a baseline-by-baseline plot is perhaps not the best way to view modern snapshot datasets. VPLOT adopts a different philosophy. It reads all the data into memory, once, and computes the model at every uv point (taking full advantage of vectorization on the Convex). After this setup, it can display different plots very fast. It is interactive: you can jump about from baseline to baseline, and view other plots such as u versus v and amplitude versus uv radius. Unlike VISPLOT, VPLOT computes the model only at the observed uv points. Thus interpolation of the model between scans is not done correctly. When VPLOT needs to display closure phases, it computes them from the baseline visibility phases; thus the input file need not contain closure phases (and if it does, they are ignored). VPLOT does not handle closure amplitudes. Example $ vplot PLOT IM1/IMA INPUT P98J1_0804_A.mrg GRID NOERRORS / UV RA HIGHLIGHT TORUN RA BL CRIMEA TORUN EXIT Parameters Some parameters can be specified when the program first starts. Thereafter, the program is controlled by commands. The parameters names VPLOT Page 2 can be abbreviated to uniqueness (minimum match). End the list of parameters with a slash (/). Parameters are: INPUT, MODFILE, MOCKDATA, PLOTFILE, NPXY, NOERRORS, GRID, GST. INPUT = "filename" : the name of the input merge-format file (e.g., INPUT = CITSCR:[TJP.B2]T1.MRG). This parameter must be specified unless a MOCKDATA file is specified; there is no default. MODFILE = "filename" : the name of a VLBI model file. This is optional; if neither MODFILE nor MOCKDATA is specified, no model will be plotted. MOCKDATA = "filename" : for plotting the results of VLBMEM, specify the name of the mock data file created by VLBMEM. If MOCKDATA is specified, MODFILE is not required. If MOCKDATA is specified and input is not, VPLOT plots the data from the merge file used by VLBMEM (its name is recorded in the MOCKDATA file). You can specify an alternate merge file with the INPUT parameter, but if you do, it must have exactly the same uv-coverage as the file for which the mock data were created. PLOTFILE = "device/type" : a standard PGPLOT device specification for the graphics device or output file (e.g., PLOTFILE = /XWIN or PLOTFILE = vplot.ps/VPS). If PLOTFILE is not specified, VPLOT will prompt for the device specification. NPXY = nx, ny (default 1, 1) : if specified, draw nx x ny graphs on each screen or each sheet of paper. NOERRORS : if this parameter is specified, VPLOT will draw data points as single dots instead of error bars. GRID : if this parameter is specified, VPLOT will draw a background grid in each graph. GST : if this parameter is specified, the default horizontal axis for time-series plots will be GST instead of UT. Commands In interactive mode, the following commands are available. Next (next baseline) [default] BAck (previous baseline) number (display specific baseline) All (display all baselines) Rad (plot amp versus uv radius) PHase (plot phase versus uv radius) PRoj pa (plot amp projected onto given PA) UVplot (plot v versus u) UVplot Amp (color indicates amplitude) UVplot Model (color indicates model amplitude) UVplot Ratio (color indicates ampl/model) UVplot Error (color indicates (AMP-MOD)/error) VPLOT Page 3 TImeline (plot sampling versus time) BL A B (plot amp/phase for baseline AB) CL A B C (plot closure for triangle ABC) (A,B,C are station names or numbers) List (list agreement factors) MODfile (read a new model file) GST (switch to GST) UT (switch to UT, default) Highlight A (highlight stn A in global plots) Highlight A B (highlight bl AB in global plots) COlor (change color scheme) EXIT (exit from program) ? (display list of commands) The normal mode of operation is to display single-baseline time-series (amplitude and phase versus time); the horizontal axis can be UT or GST, as requested by the corresponding commands. Data are displayed in green (points or error bars); the model is displayed as a red line. Note that the model is calculated only at the sampled uv points, and is linearly interpolated between points. The NEXT command (or a carriage return) displays the next baseline; BACK displays the previous baseline. To display a particular baseline, type its sequence number or use the BL command. The ALL command is intended for use in non-interactive (batch) jobs: it plots all the baselines in sequence, without pausing. To plot closure phases, use the CL command. This command has three arguments: the names or numbers of the three stations that form the required triangle. The names may be abbreviated (minimum match). UVPLOT, PROJ, RAD, and PHASE. These commands produce a general overview of the entire dataset. UVPLOT plots v versus u (i.e., displays uv coverage); RAD displays amplitude versus radius in the uv plane; PHASE displays phase versus radius in the uv plane. Data are displayed in green, model values in red. The various options of UVPLOT use color (or dot size on devices which don't support color) to indicate amplitude, model amplitude, ratio of measured amplitude to model, and error. The HIGHLIGHT command can be used to pick out either a particular station or a particular baseline in a different color (the plot must be redrawn after specifying HIGHLIGHT). This applies to UVPLOT, RAD, PROJ, PHASE. Examples: HIGHLIGHT BONN (all baselines involving BONN) HIGHLIGHT 1 7 (a specific baseline) HIGH 15 ONSA (a specific baseline) TIPLOT. This option shows the times when data are available from each station. MODFILE. To change the displayed model (or add a model if none is currently displayed) use the MODFILE command. It will prompt for the file name. VPLOT Page 4 LIST lists the baselines (sequence number and station names), showing the number of data points on each, and (if a model is selected) the amplitude and vector agreement factors for each baseline. COLOR. This command allows the user to choose a different color scheme. After typing the command, the user is placed in a parameter-input (KEYIN) environment, where she can change the RGB components of the colors. Return to the VPLOT command prompt by typing a slash (/). Colors can be saved in a file for later use with the SAVE command, or retrieved with the @ command. All parameters have three comma-separated values, corresponding to the R, G, B, color components in the range 0 (black) to 1 (maximum brightness). The parameters are: BACKGROUND (screen or window background color, default 0,0,0 = black); FRAME (used for graph frames and labels, default 1,1,1 = white); DATA (used for plotting data points, default 0,1,0 = green); MODEL (used for plotting model values, default 1,0,0 = red); GRID (used for background grids, default 0.33,0.33,0.33 = grey); HIGHLIGHT (used for baseline highlight in global plots, default 0,1,1, = cyan). Some devices do not allow all the colors to be changed. Limitations The maximum number of stations is 40, and the maximum number of (undeleted) data points (visibilities) on any baseline is 8000. Otherwise, all MERGE files with format 1 or 2 should be acceptable. The maximum number of components in a model file is 5000. Only model component types 0 (delta function) and 1 (gaussian) are implemented. History Version 1.0: 1990 Jun 7 - new program (TJP). Version 1.1: 1990 Aug 27 - add NOERR parameter, increase MAXP (TJP). Version 1.2: 1990 Sep 6 - add PHASE plot (TJP). Version 1.3: 1990 Sep 25 - add GRID, GST, ALL options (TJP). Version 1.4: 1990 Oct 14 - add MODF command (TJP). Version 1.5: 1990 Nov 12 - remove unused variables (TJP). Version 1.6: 1991 Mar 22 - allow up to 40 stations (TJP). Version 1.7: 1991 Apr 18 - PROJ and CLO plots (TJP). Version 1.8: 1991 Apr 20 - HIGHLIGHT command (TJP). Version 1.9: 1991 Jun 6 - add TI plot, increase array sizes (TJP). Version 1.10: 1991 Oct 23 - add AMPLOT (TJP). Version 1.11: 1991 Oct 31 - new UVPLOT options, annotation (TJP). Version 1.12: 1991 Nov 18 - HIGHLIGHT works for one station or two.