.\" @(#)overall	1.1	11/2/90
.\"
.\" Use Makefiles in ~ptolemy/doc
.\" to print this out.  To get this section only, as a standalone document,
.\"     % cd ~ptolemy/doc/main/pigi
.\"     % make print
.\"
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.\" out this file with SCCS (the version number should not be a number below):
.VR 1.1 "November 2, 1990"
.\"
.TI "Filter design programs"
.AU
E. A. Lee
.AE
.H1 "Introduction"
.pp
Pending the inclusion of more sophisticated filter design software with
\*(PT, this distribution includes two Fortran programs for this purpose.
These design FIR filters using the Parks-McClellan algorithm
or the window method.
The frequency sampling method can be done  directly using
\*(PT stars, as shown in the demos included with the SDF domain.
.pp
These programs can be invoked standalone or through the filter
command in pigi.  If invoked through pigi, then an xterm window
will be opened and the program started.
.pp
Filter specifications can be entered by hand or loaded from a file.
The first prompt from the program is the name of the input command file.
Simply typing return will result in manual entry.  To enter
data from a file, the data should appear in the file in exactly
the order that it would appear if it were being entered by hand,
with one question answered per line.  Unfortunately, these command
files are rather difficult to read, and not too easy to create
correctly.  It is recommended to first do manual entry, then
imitate the entries in a file.
Data can be entered in any reasonable numeric format.
.H2 "Caveats"
.pp
These are public domain Fortran program, provided for convenience, although
they are not an integral part of \*(PT.  Incorrect formatting
of data line can lead to ungraceful exits (often with a core
dump) or incorrect results.
Either program can be invoked through the \*(PT graphical interface,
in which case it is started in its own window, in the background.
Note that in this case the program always starts in your home directory.
.so optfir
.so wfir
