XY Files

These are some examples of XY files, which are simply lists of points in the plane.

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 (usually) ignored but might contain some "connection" information;
• COORDINATE LINES each contain one pair of X, Y coordinates;

There is a second version of XY files in which the blank lines are interpreted to indicate which points are connected by geometric lines.

Example XY File:

        #  Corners of a triangle
        #
        0.0  0.0
        1.0  0.0
        0.0  1.0
      

Related Data and Programs:

• The TABLE file format is the general format that includes XY files as a special 2D case;
• The XYZ file format is the analogous version of the format for the 3D case;

XY File characteristics:

• ASCII
• 2D
• No compression
• 1 image

Programs to create an XY file:

• RANDOM_DATA can produce a set of points that are randomly sampled from a given geometric shape. In cases where this was a 2D shape, the resulting output file is an XY file.
• RBOX will produce a random sample of points according to a given distribution, and over a given geometric shape. In cases where this was a 2D shape, then the resulting output file is ALMOST an XY file (you just need to delete the two initial records that list the spatial dimension and number of points.)

Programs to view an XY file:

• PLOT_POINTS will read an XY file and create an Encapsulated PostScript graphics file image of the points. It can also compute and display Voronoi diagrams and Delaunay triangulations.
• POINTS_01_PLOT is an interactive MATLAB program which can read a file containing coordinates of points in the unit square, and display an image of those points.
• POINTS_DISPLAY_MATLAB is a MATLAB program which can read a file of coordinates of points, and display an image of the points in a MATLAB graphics window.
• POINTS_DISPLAY_OPEN_GL is an interactive executable C++ program which can read a file containing 2D point coordinates, and display an image of those points using Open GL.
• VORONOI_PLOT will read an XY file (assuming that points are confined to the unit square) and create a PPMA graphics file image of the Voronoi diagram of the points.

Programs to process an XY file:

• TABLE_DELAUNAY will read an XY file and determine information about the Delaunay triangulation.
• TABLE_DIAPHONY will read an XY file and determine its diaphony.
• TABLE_DISCREPANCY will read an XY file and estimate its star discrepancy.
• TABLE_QUALITY is a program which reads a TABLE file (in particular, an XY file), and returns the "quality" of dispersion. TABLE_QUALITY is available in a C++ version, and a FORTRAN90 version, and a MATLAB version.
• TABLE_UNIFORM_NOISE will read an XY file and add uniform noise to it.
• TABLE_VORONOI will read an XY file and determine information about the Voronoi diagram. TABLE_VORONOI is available in a C++ version, and a FORTRAN90 version.

Routines to read an XY file:

• TABLE_IO is a set of routines that can read a TABLE file, or, in particular, an XY file. TABLE_IO is available in a C++ version, and a FORTRAN90 version, and a MATLAB version.

Routines to write an XY file:

• TABLE_IO is a set of routines that can write a TABLE file, or, in particular, an XY file. TABLE_IO is available in a C++ version, and a FORTRAN90 version, and a MATLAB version.

Sample XY Files:

• diamond_02_00009.xy, 9 points, whose Voronoi diagram includes a diamond;
• diamond_02_00009.png, a PNG image of the points.
• dt_10.xy, 10 points; compute the Delaunay triangulation;
• dt_10.png, a PNG image of the points.
• dt_100.xy, 100 points for which the Delaunay triangulation is to be computed;
• dt_100.png, a PNG image of the points.
• graham_10.xy, 10 points for which the convex hull is to be computed;
• graham_10.png, a PNG image of the points.
• graham_19.xy, 19 points for which the convex hull is to be computed;
• graham_19.png, a PNG image of the points.
• grid_49.xy, 49 points in a square grid.
• grid_49.png, a PNG image of the points.
• lsup_303.xy, 303 points defining the shape of Lake Superior.
• lsup_303.png, a PNG image of the points.
• points_100.xy, 100 points;
• points_100.png, a PNG image of the points.
• repeats_17.xy, 17 points, some repeated;
• repeats_17.png, a PNG image of the points.
• tri_12.xy, 12 points;
• tri_12.png, a PNG image of the points.
• tri_18.xy, 18 points;
• tri_18.png, a PNG image of the points.
• uniform_0016.xy, 16 random points in the unit square;
• uniform_0016.png, a PNG image of the points.
• uniform_0025.xy, 25 random points in the unit square;
• uniform_0025.png, a PNG image of the points.
• uniform_0036.xy, 36 random points in the unit square;
• uniform_0036.png, a PNG image of the points.
• uniform_0064.xy, 64 random points in the unit square;
• uniform_0064.png, a PNG image of the points.
• uniform_0100.xy, 100 random points in the unit square;
• uniform_0100.png, a PNG image of the points.
• uniform_0128.xy, 128 random points in the unit square;
• uniform_0128.png, a PNG image of the points.
• uniform_0256.xy, 256 random points in the unit square;
• uniform_0256.png, a PNG image of the points.

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