XY_IO
XY File Input/Output routines.

XY_IO is a FORTRAN90 library which reads and writes files in the XY, XYL and XYF formats.

XY files are a simple way of storing information about sets of points in 2D.

An XY file has a simple structure. There are three kinds of records:

COMMENT LINES begin with the character '#' and are ignored;
BLANK LINES are ignored;
COORDINATE LINES each contain one pair of X, Y coordinates;

Here is an example of an XY file containing 13 points:

#  house.xy
#
        0.000000        0.000000
        6.000000        0.000000
        6.000000        7.000000
        3.000000       10.000000
        0.000000        7.000000
        4.000000        1.000000
        5.000000        1.000000
        5.000000        4.000000
        4.000000        4.000000
        5.000000        8.000000
        5.000000       11.000000
        4.000000       11.000000
        4.000000        9.000000

Of course, in many cases, we would like to describe LINES between the points. We can add this information by including a second file, called an XYL file, which consists of a string of point indices. A line is drawn from one point to the next and so on. Each list of points is on a separate record. Thus, an XYL file associated with the above XY file might be:

#  house.xyl
#
 1 2 3 4 5 1
 6 7 8 9 6
 10 11 12 13

We might also like to describe FACES defined by the points. We can add this information by including a file, called an XYF file, which consists of a string of point indices. A face is defined by listing in counterclockwise order the vertices that lie on it. No terminating "-1" is needed, and the first vertex is not repeated as the final vertex. Thus, an XYF file associated with the above XY file might be:

#  house.xyf
#
 1 2 3 4 5
 6 7 8 9
 10 11 12 13

Licensing:

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

Languages:

XY_IO is available in a C++ version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

CIRCLE_ARC_GRID, a FORTRAN90 program which computes points equally spaced on a circular arc, and writes them to an XY file;

GRF_TO_XYL, a FORTRAN90 program which converts information describing the adjacency and embedding of an abstract graph from GRF to XYL format.

TABLE, a data directory which contains examples of TABLE files, a simple format for N points in M dimensions;

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

XY_DISPLAY, a MATLAB program which reads an XY file containing the coordinates of points in 2D, and displays a plot of the points in a MATLAB graphics window;

XY_DISPLAY_OPENGL, a C++ program which reads an XY file of 2D point coordinates, and displays an image of those points using OpenGL.

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

XYF_DISPLAY, a MATLAB program which reads XYF information defining points and faces in 2D, and displays an image using MATLAB.

XYF_DISPLAY_OPENGL, a C++ program which reads XYF information defining points and faces in 2D, and displays an image using OpenGL.

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.

XYZ_IO, a FORTRAN90 library which reads and writes XYZ files, a simple 3D graphics point format.

Source Code:

xy_io.f90, the source code.

Examples and Tests:

xy_io_test.f90, a sample calling program.
xy_io_test.txt, the output file.
xy_io_test01.xy, an XY file created by the example program.
xy_io_test02.xy, an XY file created by the example program.
house.xy, an XY file of points created by the example program.
house.xyl, an XYL file of lines created by the example program.
annulus.xy, an XY file of points created by the example program.
annulus.xyf, an XYF file of lines created by the example program.

List of Routines:

CH_CAP capitalizes a single character.
CH_EQI is a case insensitive comparison of two characters for equality.
CH_TO_DIGIT returns the integer value of a base 10 digit.
GET_UNIT returns a free FORTRAN unit number.
S_TO_I4 reads an integer value from a string.
S_TO_I4VEC reads an integer vector from a string.
S_TO_R8 reads an R8 value from a string.
S_TO_R8VEC reads an R8VEC from a string.
S_WORD_COUNT counts the number of "words" in a string.
TIMESTAMP prints the current YMDHMS date as a time stamp.
TIMESTRING writes the current YMDHMS date into a string.
XY_DATA_PRINT prints the data of an XY file.
XY_DATA_READ reads data from an XY file.
XY_DATA_WRITE writes the data of an XY file.
XY_EXAMPLE sets up sample XY data suitable for an XY file.
XY_HEADER_PRINT prints the header of an XY file.
XY_HEADER_READ determines the number of pairs of data in an XY file.
XY_HEADER_WRITE writes the header of an XY file.
XY_READ_TEST tests the XY file read routines.
XY_WRITE writes an XY file.
XY_WRITE_TEST tests the XY write routines.
XYF_DATA_PRINT prints the data of an XYF file.
XYF_DATA_READ reads the data in an XYF file.
XYF_DATA_WRITE writes the data of an XYF file.
XYF_EXAMPLE sets data suitable for a pair of XY and XYF files.
XYF_EXAMPLE_SIZE sizes the data to be created by XYF_EXAMPLE.
XYF_HEADER_PRINT prints the header of an XYF file.
XYF_HEADER_READ determines the number of face items in an XZF file.
XYF_HEADER_WRITE writes the header of an XYF file.
XYF_WRITE writes an XYF file.
XYL_DATA_PRINT prints the data of an XYL file.
XYL_DATA_READ reads the data in an XYL file.
XYL_DATA_WRITE writes the data of an XYL file.
XYL_EXAMPLE sets data suitable for a pair of XY and XYL files.
XYL_EXAMPLE_SIZE sizes the data to be created by XYL_EXAMPLE.
XYL_HEADER_PRINT prints the header of an XYL file.
XYL_HEADER_READ determines the number of line items in 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.

Last revised on 08 January 2009.