Handling of Plotfiles

Plotting in MIDAS will create a MIDAS plotfile which contains all essential plot information. By default this plotfile (metafile)  is always created by the execution of the main plot commands. The plotfile will carry the name of the data structure that has been plotted: the name of a frame, table, descriptor or keyword. The plotfile has the extension ``.plt''. MIDAS keeps track of what the user has plotted. The SHOW/GRAPH command shows the user which is the last created plotfile. Subsequent overplot commands will append to this plotfile. Names of plotfiles are a composition of the device names that is currently assigned and the MIDAS session number. As an example, take the situation were the user runs MIDAS under the unit number 04 and the graphics window 1 (graph_wnd1) is assigned. In this case all plots created will be stored in the file graph_wnd104.plt. If the device ``lp'' was assigned, plot files will go into the file lp04.plt. Names of plot files are unique and do not have version numbers. Hence, MIDAS will delete an old plotfile if a new one with the same name is created. With the command SHOW/GRAPH you can display the name of the plot file.

There are several ways to obtain a hardcopy  of a plot. Below you will find a few examples.

1.

The user works with a graphic terminal or a workstation and has made this plot on the graphic terminal first. He/she can now send the plot to a hardcopy device using the COPY/GRA command.
Example:

MIDAS 001> PLOT/TABLE mytable :velocity :distance
MIDAS 002> COPY/GRAPH LASER

2.

The user does not have a graphics terminal (or does not want to use it), and wants to dump his plot directly onto a hardcopy device. In this case, the hardcopy device has to be assigned first as the output device by the ASSIGN/GRAPH command. Now all the plot(s) (including the overplot !!!) will be sent directly to the hardcopy device.
Example:

MIDAS 003> ASSIGN/GRAPH LASER ! assign LASER as output device
MIDAS 004> PLOT/TABLE mytable :velocity :distance ! make plot

3.

In a MIDAS plot command sequence (with many e.g. OVERPLOT and LABEL commands) intermediate output is not always wanted, in some cases even undesirable. In order to switch off the direct routing of plots to a device users can specify the extra switch NOSPOOL  in the ASSIGN/GRAPH command. Using this switch the plotfile(s) will be stored on disk first. Once the user has finished his sequence of plot commands, he/she can create the complete plot on the hardcopy device using the command COPY/GRAPH. Intermediate results can be obtained using the same command.
Example:

MIDAS 005> ASSIGN/GRAP LASER NOSPOOL ! plot file, don't send
MIDAS 006> PLOT/ROW frame [@100,@150:@150,@250] 20.0,20.0
MIDAS 007> OVERPLOT/TABLE table #1 ! overplot
MIDAS 008> LABEL/GRAPHIC "THIS IS AN EXAMPLE" 90 4 400,300
MIDAS 009> COPY/GRAPH LASER ! send the plot file

4.

The user wants to send a previously created MIDAS plotfile ( e.g. ``midas.plt'', and different from the last created plotfile) to a device.
Example:

MIDAS 010> COPY/GRAPH LASER frame.plt ! send plotfile to LASER

As can be seen in section 6.1.9, in most cases the user can produce a plot with certain scales of the x- and y-axis. In the current version routing the plot file (with COPY/GRAPH) to a device different from the one pre-specified (with the ASSIGN/GRAP command) may lead to incorrect scales. In case the pre-specified device is the same as the device to which the plot is sent the scales will be correct.
Example:

MIDAS 005> ASSIGN/GRAPH VERSA NOSPOOL
MIDAS 006> PLOT/ROW image [@100,@150:@150,@250] 20.0,20.0
MIDAS 007> OVERPLOT/TABLE table #1
MIDAS 008> LABEL/GRAPHIC "THIS IS A EXAMPLE" 90 4 400,300
MIDAS 009> COPY/GRAPH LASER ! plot will have incorrect scales
MIDAS 010> COPY/GRAP VERSA ! with correct scales