A>sst
The SST program will be loaded into memory (this takes about 30 seconds) and the following message appears on the screen:
SST - Statistical Software Tools Version 1.0, copyright 1985, 1986 by J.A. Dubin and R.D. Rivers
Your are now ready to compute.
C>cd \sst C>sst
and the message above should appear on the screen.
You are in interactive mode. SST will execute commands one at a time as you issue them. Each command is executed after a carriage return (the key marked <Enter>) has been pressed.
Sometimes a command will not fit on a single line. To continue a SST command onto the next line, type a backslash (`\') followed by a carriage return and continue typing. You can repeat this procedure as many times as necessary until you have finished typing the command.
The typical SST command consists of a command name followed by various subops. The command name tells SST what procedure it is to perform. The subops tell it what variables you want it to use, options, and other details of the procedure. Subops are of two forms. Some subops are just "flags". Others take arguments such as which observations you will be dealing with.
RANCE command. SST is a
very flexible program and it tries to accomodate your needs. You may have
only a few variables, but many observations on each variable. On the other
hand, you may have many variables, but only a few observations. To store
datasets efficiently, SST needs to know roughly how many observations you
will be dealing with and the RANCE statement provides this
information. For example:
range obs[1-100]
tells SST that you will be using 100 observations. It is not
necessary to know exactly how many observations you will be using (any
reasonable guess will do) nor does specifying one obseration range
(with the OBS subop) prevent you from changing it later to a larger
or smaller range statement. If you omit the RANCE command, SST may
become rather slow for some procedures, because it assumes that you
will have 8000 observations on each variable. It is a good habit to
always issue a RANCE statement as the first command of any SST
session. The RANCE command also serves the purpose of determining
which observations will be used for statistical procedures. For
example, at some point in an SST session, you may decide that only
observations 100 through 200 and 500 through 600 should be used for
subsequent statistical procedures. Give the command:
range obs[100-200,500-600]
and only these observations will be used until you issue another
RANCE statement. Subsequent RANCE statements may either
enlarge, contract, or completely change the range of observations used for
statistical procedures. The RANCE statement can also be set to
include all observations satisfying a logical condition by using the IF
subop. Logical expressions in SST are described in detail in Chapter 4 of
the User's Guide, but their use is not complicated. For example, if
x is a variable stored in memory, you can pick out all observations
for which x is positive by giving the RANCE command:
range if[x>0]
Until another RANCE statement is issued, only those observations for
which the variable x is positive will be employed.
If you don't remember an SST command name, type:
help
and SST will provide a complete list of command names. If you don't remember the syntax for the command, type `help' followed by the command name:
help command_name
and SST responds with a short summary of the command syntax. Detailed information about how the command works and examples may be found in the User's Guide and Reference Manual. The notation used to describe the syntax of SST commands by the on-line help facility (as well as in the SST Reference Manual) is the following: optional subops are enclosed in braces (`{' and ` 2') while the kind of argument used by a subop (e.g., number, variable list, etc.) replaces the subop argument inside brackets; optional subops which do not take arguments (flags) are just enclosed in braces. If you use a subop which takes an argument, you must type the brackets. Do not type braces around optional subops. (Braces have a special meaning to SST that is explained in the Chapter 8).
Some users prefer to be prompted for subops. If you type an incomplete command leaving out a required subop, SST will prompt you for missing subops. For example, type just a command name, and SST will supply the names of required subops one at a time. You supply just the arguments to the subop (that is, don't type subop name or the brackets around the arguments as you would normally). When you have entered all the required subops, SST then gives you a chance to add optional subops by asking you for options. You type optional subops as you normally would (including brackets). The subop prompting feature allows you to operate SST largely as a menu-driven program.
SST periodically checks to see if you want it to stop processing a command. For example, you may have started to print some data and then become impatient. If you depress the <Ctrl> and <Scroll Lock> keys simultaneously, SST will stop processing the current command and allow you to enter a new command.
To return to DOS from SST, just type:
quit
The QUIT command eliminates all scratch files created during the SST
session and properly terminates SST processing.
There are two ways to execute a batch file. First, from the DOS prompt you may invoke SST with a filename:
A>sst file.cmd
SST will automatically execute the commands in the file file.cmd
without further prompting. Alternatively, you may start SST in
interactive mode and at some point during your SST session (perhaps as
the first command) give the RUN command:
run file.cmd
If the last command in your SST command file is the QUIT command, SST
will return to DOS. Otherwise, SST allows you to continue
interactively. You may, for example, RUN another command file after
SST has finished processing the first command file.
If a command file is specified without an extension (either in the RUN command or when SST is started), SST assumes the extension `.cmd'. You may use other extensions for command files, but in this case the extension must be specified. If the command file has no extension, type the filename followed by a period with no extension.
Interactive model allows you to experiment with your data. Based on the results of one statistical procedure you can choose what to do next. Typing commands, however, is rather tedious, and sometimes it's easier to use the editing features of a word processor to create a file containing a large number of commands.
However batch mode has disadvantages. It requires one to "plan ahead" by writing out a sequence of commands. If the program contains an error, you can fix the error by altering the commands using a word processor and then reexecute the SST program. This means that earlier commands (that were fine all along) now have to be reexecuted or one has to specify that these particular commands should not be executed. Either way takes time, and it may be quicker to use interactive mode in some cases.
We prefer to mix interactive and batch mode. We keep some frequently executed commands in batch files which can be run whenever needed without retyping. The spooling feature, described below, can also be used to simplify input.
There are only two commands which one uses in batch mode that one
doesn't use in interactive mode. The first, PAUSE, causes the program
to stop execution and display a message Press return to continue on
the screen. Execution continues when a carriage return is entered. As
explained above in the DOS unnumberedsec, one can stop the program at any
time by depressing the <Ctrl> and <NumLock> keys simultaneously. The
PAUSE command stops the program at a predetermined point. This
eliminates the need to watch the screen to stop the program at the
desired point.
If you created an SST command file some time ago, you may have
forgotten the purpose of certain procedures. SST allows you to add
comments to your command files with the REM command. Whatever fol-
lows the REM command is printed on the screen as you type it. Thus:
rem regression without a constant
will appear on the screen, but no action is taken. In editing a command file, sometimes it is better to "comment out" commands that you don't want executed, rather than delete them. You can use a word processor or editor to add REM in front of commands that you do not want executed so that these commands will be ignored by SST.
After using SST for awhile, we are confident that you won't want to
leave SST for very long, so we have provided a facility for executing
other programs without having to leave SST with the SYS command.
SYS allows you to leave SST temporarily to do other tasks and then to
return to SST, with all your data preserved in the same state that you
left them.
The SYS command is extremely useful. Although SYS can be used
in batch mode, the most common use is in interactive mode. Any DOS command
can be executed with SYS. For example, to obtain a directory without
leaving sst, type:
sys dir
and the directory appears on the screen, followed by the SST prompt, and you can continue your SST session.
Another common use of the SYS command is to move between SST and a
word processor to create and edit SST commands. Suppose you normally
access your word processor by typing `wp'. To access your word
processor from within SST, one would simply enter (after the SST
prompt):
sys wp
You can now use your word processor as usual. When you exit the word processor, you will be put back into SST. Thus a common sequence would be:
sys wp file.cmd
You are now in your word processor and you can edit the file of SST
commands, file.cmd. Once you have finished editing the file and have
returned to SST, you can RUN the command file:
run file.cmd
To execute more than one command outside of SST, type:
sys command
and the DOS prompt appears. When you have finished executing DOS commands and other programs, type:
A>exit
and you will be returned to SST with everything in the state that you left it.
A few words of caution about the SYS command. First, not all programs
can be executed using SYS. Programs with a nonstandard interface to
the operating system, may cause the SST session to be aborted. All
DOS commands are guaranteed to work and we have found that many
popular programs can be executed this way. On the other hand, we
cannot guarantee that any non-DOS command will work and it is prudent
to try executing the program from within SST when nothing of
importance can be lost, before using this facility.
Second, it is possible to fill up the memory of your computer to the point that there is not enough room to load the program that you want to execute. If this happens, SST will give you an error message explaining the situation and return you to the SST session. No harm is done, but don't be surprised if this happens.
SST output goes directly to the screen unless you specify otherwise.
Unfortunately this means that results tend to scroll by too fast to
read. There are several options to deal with this problem. As
explained above, in batch mode, you can stop the execution of SST
commands with the PAUSE command. You can also stop the execution of
commands, in either batch or interactive mode, by using the depressing
the <Ctrl> and <NumLock> keys simultaneously. To restart execution,
press the same keys again.
For some purposes, neither of these is totally satisfactory. PAUSE
doesn't allow you to stop the execution within a command, so a PAUSE
after a command that produces several screens of output will only stop
the screen at the last screen. You can study earlier output by
stopping the screen using the <Ctrl><Numlock> sequence, but this
requires one some dexterity to catch SST at just the right moments.
The best solution to this problem is to make a copy of what appears on
the screen with the SPOOL command. To save a record of an SST session,
supply a filename in the FILE subop of the SPOOL command:
spool file[filename]
All output from this point on will be saved in the file you specified. To turn off spooling, type:
spool off
SST allows you to spool your commands to another file from output produced by the program. This turns out to be a very convenient feature since it allows you to create a batch file of SST commands which will reproduce your SST interactive session. To save commands only in a file, type:
spool file[filename] cmd
and your commands, from this point on, will be saved in the file specified. To turn command spooling off, give the command:
spool cmd off
while:
spool out off
would turn off output spooling only. (If neither CMD or OUT
is specified, OFF turns off all spooling.) Thus, you can have up to two
spool files open at once. To see which spool files are on at present, type:
spool
and SST tells you what is (or is not) currently being spooled.
SST allows several combinations of spooling depending on what subops are supplied. The possible combinations are:
CMD or OUT is specified, both commands
and output are spooled to the file specified in filename.
CMD alone is specified, only commands are saved.
OUT alone is specified, only output will be saved. (Your
commands appear in the OUT file preceded by the SST prompt)
We recommend that you give spool files the extensions `.out' and
`.cmd' as appropriate. The file can be examined while still in SST by
using the SYS command. For example, if you had spooled to the file
file.out, this file could be displayed on the screen by entering:
sys type file.out
This allows your to recall what happened earlier during your SST session. You may also want to rerun some commands, perhaps with a few minor changes. We suggest that you spool commands to a file:
spool file[file.cmd] cmd
When you decide that you want to rerun some commands, turn off
command spooling and RUN the command file for an instant replay of
your SST session:
spool cmd off run file
(The `.cmd' extension is assumed for command files by the RUN
command.)
The spooled file can be edited using a text processor. This is
often the easiest incorporate SST output into reports. You can spool
the output to a file, edit out the unneeded output, and then
incorporate the output into your report using your word processor.
SPOOL appends output to whatever file you specify. Thus spooling can
be turned on and off selectively if you don't want to save everything
that happens during your SST session.
SPOOL allows you to watch output as it comes to the screen while the
same output is being saved in a file. If you don't want to see output on
the screen, SST allows you to use a command line option to send all output
to a file and suppress printing on the screen. This option can only be used
in conjunction with batch input on the command line. If file.cmd
contains your SST commands and you would like to send output to the file
sst.out, invoke SST by:
sst file.cmd -o sst.out
The -o flag tells SST that the next command line argument will be a file for output.
If you want to know how long SST took to perform an operation, use the
TIME command. One can include a TIME subop in most every
command. It prints the elapsed time between the time SST received a
command and finished executing it. The time required to print output on
the screen is included.
