You may not have realized while going through our simple example that every detail of the graphs that you were creating could be modified. That's because physica provides a pretty reasonable set of default settings for things like line widths, character sizes, layout of the graph on the page, etc. However, should you be unhappy with any of these defaults, physica allows you to change them. The general method of changing something is the command
PHYSICA: set parameter value
which has over a hundred different parameters that specify every minute detail of the appearance of the graph, from the frame placement on the page, to the angle of the axis tics. All parameters have names that are no more than six-character long (Fortran experts will recognize the origin of this convention), and an attempt has been made to keep the names logically related. All parameters that are integers begin with n; a set of parameters pertaining to y-axis is identical to the ones for the x-axis with letter y in place of x, etc. For example, nlxinc and nlyinc are the numbers of large x or y-axis increments, i.e. the major divisions of the appropriate axis. Also, the way of modifying all parameters is exactly the same: if you specify parameter but not the new value, the current value is reported, you are prompted for the new one, and entering a carriage return alone retains the old value. In addition, all parameters that define length or size of something can be specified in graph units or in percent of the page size; you choose the latter by prepending % to the parameter name.
Some useful examples:
Other parameters in this ``family'': xuaxis, ylaxis, and yuaxis.
PHYSICA: set
name { value(s) } >> %xlaxis 18
name { value(s) } >> %xuaxis 95
name { value(s) } >> box 0
name { value(s) } >> lintyp 7
name { value(s) } >>
PHYSICA:
with a blank line at the end terminating the current set command. In a macro file, of course, you would not enter the text of the prompt (name ... >>) but a blank line to terminate a multiple set command would still be needed.
There are a few commands that affect the settings, but are important enough to deserve their own physica command. A good example is scales command which allows you to specify explicitly the x and y-axis scales and number of divisions on each (physica defaults to scales that include all of the data, and determines an appropriate number of divisions automatically; most of the time it does a pretty good job). In principle, you could achieve the effects of a single scales command with a series of set commands, explicitly changing such parameters as xauto, xmin, xmax, nlxinc, nsxinc, nxdig, nxdec, etc., but this is much less convenient. For more information, try help scales.