GRF_TO_XYL
Convert a GRF file to XYL format

GRF_TO_XYL is a FORTRAN90 program which converts information about an abstract graph from GRF to XYL format.

The GRF format is used by the Combinatorica program. It records, for each node of the graph, the (X,Y) coordinates of each node in a drawing of the graph, and the nodes which are adjacent to that node.

In the XYL format, an XY file stores the (X,Y) coordinates of points, and an XYL file stores lists of node indices to be connected by lines.

Usage:

grf_to_xyl file.grf

• file.grf is the GRF file;

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Languages:

GRF_TO_XYL is available in a FORTRAN90 version.

Related Data and Programs:

GRAFFITI, a dataset directory which contains 195 abstract graphs, with adjacency and embedding information, stored in the GRF format.

GRAPH_REPRESENTATION, a data directory which contains examples of ways of representing abstract mathematical graphs

GRF, a data directory which contains a description of the GRF format and some examples.

GRF_DISPLAY, a MATLAB program which reads a GRF file defining a mathematical graph and displays it in the MATLAB graphics window.

GRF_DISPLAY_OPENGL, a C++ program which reads a GRF file defining a mathematical graph and displays it in an OpenGL graphics window.

GRF_IO, a FORTRAN90 library which reads and writes GRF files.

GRF_TO_EPS, a FORTRAN90 program which converts a GRF file to EPS format;

XY_IO, a FORTRAN90 library which reads and writes XY, XYF and XYL files.

XYL, a data directory which contains examples of XYL files, a simple 2D graphics point and line format;

XYL_DISPLAY, a MATLAB program which reads XYL information defining points and lines in 2D, and displays an image using MATLAB.

XYL_DISPLAY_OPENGL, a C++ program which reads XYL information defining points and lines in 2D, and displays an image using OpenGL.

Reference:

1. Stephen Skiena,
   Implementing Discrete Mathematics: Combinatorics and Graph Theory in Mathematica,
   Addison Wesley, 1990.
2. Peter Eades, Ian Fogg, David Kelly,
   SPREMB: A System for Developing Graph Algorithms,
   Congressus Numerantium,
   Volume 66, December 1988.

Source Code:

• grf_to_xyl.f90, the source code.

Examples and Tests:

COXETER is the Coxeter graph:

• coxeter.grf, the GRF file.
• coxeter.xy, the XY file.
• coxeter.xyl, the XYL file.
• coxeter.png, a PNG image created by XYL_DISPLAY_OPEN_GL.

K5 is the complete graph on 5 nodes:

• k5.grf, the GRF file.
• k5.xy, the XY file.
• k5.xyl, the XYL file.
• k5.png, a PNG image created by XYL_DISPLAY_OPEN_GL.

PETERSEN is the Petersen graph:

• petersen.grf, the GRF file.
• petersen.xy, the XY file.
• petersen.xyl, the XYL file.
• petersen.png, a PNG image created by XYL_DISPLAY_OPEN_GL.

TUTTE is the Tutte graph:

• tutte.grf, the GRF file.
• tutte.xy, the XY file.
• tutte.xyl, the XYL file.
• tutte.png, a PNG image created by XYL_DISPLAY_OPEN_GL.

List of Routines:

• MAIN is the main program for GRF_TO_XYL.
• CH_CAP capitalizes a single character.
• CH_EQI is a case insensitive comparison of two characters for equality.
• CH_TO_DIGIT returns the integer ( kind = 4 ) value of a base 10 digit.
• FILE_NAME_EXT_GET determines the "extension" of a file name.
• FILE_NAME_EXT_SWAP replaces the current "extension" of a file name.
• GET_UNIT returns a free FORTRAN unit number.
• GRF_DATA_READ reads the data of a GRF file.
• GRF_HEADER_READ reads the header of a GRF file.
• GRF_TO_XYL converts GRF information to XYL information.
• S_EQI is a case insensitive comparison of two strings for equality.
• S_INDEX_LAST finds the LAST occurrence of a given substring.
• S_TO_I4 reads an integer value from a string.
• S_TO_R8 reads an R8 value from a string.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• TIMESTRING writes the current YMDHMS date into a string.
• XY_DATA_WRITE writes the data of an XY file.
• XY_HEADER_WRITE writes the header of an XY file.
• XY_WRITE writes an XY file.
• XYL_DATA_WRITE writes the data of an XYL file.
• XYL_HEADER_WRITE writes the header of an XYL file.
• XYL_WRITE writes an XYL file.

You can go up one level to the FORTRAN90 source codes.