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Docs: ERPSS System Tour
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The Event-Related Potential Software System (ERPSS) is a set of programs and data formats which allow versatile analysis of neurophysiological data. Signal averaging, plotting, signal processing, and statistical analysis are among the capabilities of the system. The ERPSS design represents an evolution of many previous programs and data formats, and incorporates suggestions and analysis techniques proposed by many users over a period of more than ten years.
ERPSS data are stored in a standardized format that allows flexible analysis after collection and consistent manipulation by various programs. The user interface is relatively simple and consistent; the programs are written so that they can be easily ported to various machines, and the data are automatically adjusted to accommodate differences in the underlying hardware when transported between machines. The software is written primarily in the C programming language, and performs best in a UNIX/Linux operating system environment.
This document describes the various ERPSS programs that are available, their capabilities, and their functions in the process of collecting and analyzing data in an experimental setting. It is designed to give a quick overview, directing the user to more detailed documentation for various programs and providing a framework that allows one to understand the rationale for the organization and design of the ERP software system.
The ERP software system was designed to function in a UNIX environment, and as such relies on the availability of a number of utilities that are part of standard UNIX. For example, many ERPSS programs employ text files that contain parameters and options that control the operation of the data processing by a program. Hence, it is almost mandatory that a powerful editor be available to create and edit these text files - the ability to powerfully manipulate text files allows simpler and more easily written programs to attain the capabilities of more complicated and difficult-to-use programs. However, this does not preclude the use of ERPSS programs in foreign environments; as long as the function of the these ancillary utilities can be somehow accomplished, the ERPSS programs will perform well. Nonetheless, the maximum potential of the system is most easily realized in a UNIX environment, where the capabilities of vi, sed, awk, and shell scripts (i.e., sh, tcsh,.. ) are available.
A corollary of this approach to the ERPSS design is that the user will achieve maximum results with a minimum of effort by mastering the operating system under which the ERPSS programs run. Thus, in a UNIX environment, familiarity with a text editor and a shell is quite important. One must know how to log in to the system, specify filenames, print text files, operate storage and backup devices, create, copy, delete, and rename files, etc. Knowledge of and facility with additional standard UNIX utilities will further ease the use of the ERP software system. The bottom line here is that to utilize the ERPSS programs effectively, one must first gain a good working knowledge of the operating system environment. At that point, this document will become meaningful and useful.
The first order of business is to describe the manner in which the various ERPSS programs are documented and how those documents can be accessed. There are two main formats for ERPSS documentation: "man pages", and "user's manuals". "Man pages" refer to specific descriptions for each ERPSS program and are kept online in the same manner as the standard UNIX manual; these writeups are intended to be sufficient to allow one to use a program. Since the format of the UNIX manual and the ERPSS manual are similar, references to ERPSS manual entries normally include a suffix with the letter "E" followed by the section number in the ERPSS manual. This allows one to distinguish entries in the standard UNIX manual from those in the ERPSS manual. Some programs, however, are reasonably complicated and require a longer, more detailed explanation. These "user's manuals" will be made available online for easy access, and hardcopies may be produced as needed.
Several programs for presenting stimuli and acquiring ERPSS data have been written for PCs running in a Windows multi-threaded operating system, and documentation for these programs is available in binders that can be found in the laboratories. The text files containing these documents can be found in /epl/erpss/doc/ibm. They are also available online here.
The ERPSS manual is divided into eight sections or "chapters", each containing different classes of information about the ERP software system. These sections are modeled loosely after the UNIX system manual. Here is the classification scheme for the sections of the ERPSS manual:
Sometimes it is difficult to remember what specific programs are available to perform certain functions. In this case, the apropos (1) command can be used. The manual page for every program contains a short, one-line description, and apropos finds the names of programs whose short descriptions contain a specific keyword. For example, to find the name of programs that might have something to do with averaging, one could try:
apropos average
It is sometimes necessary to try several different keywords
before the desired program is found. In addition, this program
searches through all sections of the manual, and many of the
manual items printed by apropos therefore correspond to items that
are not user programs.
Sometimes one remembers a name, but can't recall the function. The program whatis (1) prints the short description corresponding to name supplied as an argument.
On occasion one wishes a hard-copy of the up-to-date version of a manual page. This is within the capabilities of man (1). Why don't you try the following:
man -t man
Now you have your very own hardcopy of the man manpage for you
to study.
Some programs require relatively complex documents to describe their functions, file formats, and use. These documents are termed "user's manuals" and are generally more tutorial than the manual page that describes the program. These user's manuals are available here; one can peruse this area of the ERPSS file hierarchy as desired.