.TH NEATO 1 "12 August 1994"
.SH NAME
neato \- preprocessor for drawing undirected graphs
.SH SYNOPSIS
\fBneato\fR [\fB\-G\fIname=value\fR]
[\fB\-N\fIname=value\fR]
[\-E\fIname=value\fR]
[\fB\-T\fIlang\fR]
[\fB\-l \fIlibfile\fR]
[\fB\-o \fIoutfile\fR]
[\fB\-v\fR]
[files]
.SH DESCRIPTION
.I neato
draws undirected graphs using ``spring'' models (see Kamada and Kawai,
Information Processing Letters 31:1, April 1989).  Input files must be
formatted in the
.I dot
attributed graph language.
By default, the output of
.I neato
is the input graph with layout coordinates appended.
To make Postscript, use the \fB\-Tps\fP option.
FrameMaker MIF (\fB-Tmif\fP), HPGL (\fB-Thpgl\fP),
and GIF (\fB-Tgif\fP) are other choices.
.PP
Here is a brief synopsis of the graph language.
.PP
\fBgraph \fIname\fP { \fIstatement-list\fP }\fR is the top level graph.
Statements may be:
.PP
\fIname\fB=\fIval\fB;\fR
.br
\fBnode [\fIname\fB=\fIval\fB];\fR
.br
\fBedge [\fIname\fB=\fIval\fB];\fR
Set the default graph, node, or edge attribute \fIname\fP to \fIval\fP.
Any subgraph, node, or edge specified after one of these statements
inherits these attributes.
.PP
\fBn0 [\fIname0=val0,name1=val1,...\fB];\fR
Creates node \fBn0\fP if it does not exist,
and sets its attributes according to the optional list. 
.PP
\fBn0 \-\- n1 \-\- \fI...\fB \-\- nn [\fIname0=val0,name1=val1,...\fB];\fR
Creates edges between nodes \fBn0\fP, \fBn1\fP, ..., \fBnn\fP and optionally
sets the given attributes.  Creates nodes as necessary.
.PP
\fBsubgraph \fIname\fB { \fIstatement-list \fB}\fR
Creates a subgraph.  A subgraph may appear in place of
an individual node within an edge statement.
The \fBsubgraph \fIname\fR part is optional. If missing,
the subgraph is given an internal name.
.PP
While attribute names and values may be arbitrary strings,
certain fixed attributes control \fIneato\fP's layout algorithm,
as next described.
.SH "GRAPH ATTRIBUTES"
Refer to \fIdot\fP(1) options to control the layout size.
In addition, \fIneato\fP recognizes the following:
.PP
\fBstart=\fIval\fR.  Requests random initial placement and seeds
the random number generator.  If \fIval\fP is not an integer,
the process ID or current time is used as the seed.
.PP
\fBepsilon=\fIn\fR.  Sets the cutoff for the solver.
The default is 0.1.
.PP
.SH "NODE ATTRIBUTES"
Refer to \fIdot\fP(1) for options to control node labels, shapes,
sizes, colors, fonts, etc.
.SH "EDGE ATTRIBUTES"
Refer to \fIdot\fP(1) for options to control edge line style
and labels.  In addition \fIneato\fP recognizes the following:
.PP
\fBw=\fIf\fR sets the weight (spring constant) of an edge
to the given floating point value.  The default is 1.0;
greater values make the edge tend more toward its optimal length.
.PP
\fBlen=\fIf\fR sets the optimal length of an edge.
The default is 1.0.
.SH "COMMAND LINE OPTIONS"
\fB\-v\fP (verbose) prints delta energy every 100th iteration.
.SH "EXAMPLE"
.nf
\f5graph test123 {
        a \-\- b \-\- c;
        a \-\- {x y};
        x \-\- c [w=10.0];
        x \-\- y [w=5.0,len=3];
}\fP
.fi
.SH "CAVEATS"
Because unconstrained optimization is employed, node boxes can
possibly overlap or touch unrelated edges.  All existing
spring embedders seem to have this limitation. 
.PP
Apparently reasonable attempts to pin nodes or adjust edge lengths
and weights can cause instability.
.SH "SEE ALSO"
.BR dot (1)
.br
S. C. North, "NEATO User's Manual".
Available on research.att.com in dist/drawdag/neatodoc.ps.Z.