TABLE_MERGE
Merge Duplicate or Nearby Points.

TABLE_MERGE is a FORTRAN90 program which can be used to remove duplicate points from a file, or to merge points that are very close.

Initially, each point is in its own cluster. If two clusters are separated by a distance of less than the tolerance, then they are replaced by one cluster, whose representative point is the weighted sum of the two cluster representatives.

The clusters are repeatedly processed until all clusters are separated by a distance of at least the tolerance.

This algorithm may be useful when a dataset containing a number of points is given, and

• duplicate points must be removed (in this case, a value of TOLERANCE = 0 will work)
• OR, points that are very close to each other should be discarded. In this case, a "small" value of TOLERANCE is appropriate.

Note that this procedure depends on the ordering of the points. If you have three points A < B < C separated by slightly less than the tolerance, then A and B will be merged or B and C will be merged, depending on the labels of the nodes. Thus this process is not a strictly geometric procedure.

Secondly, it should be obvious that the procedure may return points that were not input points, because of the use of centroids.

Third, this procedure does guarantee that the output points are separated by more than TOLERANCE units of distance.

Usage:

table_merge table_file tolerance

reads the points in table_file, removes duplicates, replaces points that are within tolerance of each other by a centroid, and writes out the revised file.

Licensing:

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

Languages:

TABLE_MERGE is available in a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

POINT_MERGE, a FORTRAN90 library which considers N points in M dimensional space, and counts or indexes the unique or "tolerably unique" items.

TABLE_BARPLOT_PPMA, a FORTRAN90 program which reads a table file and creates an ASCII Portable Pixel Map (PPM) bargraph of the data.

TABLE_BORDER, a FORTRAN90 program which adds a border (of zero values) to a table file.

TABLE_COLUMNS, a FORTRAN90 program which extracts specific columns of data from a table file.

TABLE_COLUMNS_PERMUTE, a FORTRAN90 program which permutes the columns of a table file.

TABLE_DELAUNAY, a FORTRAN90 program which computes the Delaunay triangulation of a set of points.

TABLE_HISTOGRAM, a FORTRAN90 program which makes a histogram of a set of points stored in a table file.

TABLE_IO, a FORTRAN90 library which supplies the routines used to read the TABLE file.

TABLE_LATINIZE, a FORTRAN90 program which reads a file of points and creates a "latinized" version by adjusting the data.

TABLE_ORTHONORMALIZE, a FORTRAN90 program which reads a file of points and orthonormalizes the columns.

TABLE_QUALITY, a FORTRAN90 program which reads a file of points and computes the quality of dispersion.

TABLE_RECORD_MATCH, a FORTRAN90 program which finds close records in a table file.

TABLE_SCALE, a FORTRAN90 program which multiplies the entries of a table file by a scale vector.

TABLE_SHIFT, a FORTRAN90 program which shifts the entries of a table file by a shift vector.

TABLE_STATS, a FORTRAN90 program which reads a table file and compute certain statistics.

TABLE_TET_MESH, a FORTRAN90 program which reads a table file of 3D data, and compute a tetrahedral mesh.

TABLE_TOP, a FORTRAN90 program which reads a table file of M-dimensional data and makes a table of plots of all pairs of coordinates.

TABLE_UNBORDER, a FORTRAN90 program which removes the border from a table file.

TABLE_UNIFORM_NOISE, a FORTRAN90 program which adds a uniform noise term to the data in a table file.

TABLE_VORONOI, a FORTRAN90 program which computes information about the Voronoi diagram of the points.

Source Code:

• table_merge.f90, the source code.
• table_merge.sh, commands to compile the source code.

Examples and Tests:

• uniform_02_00100.txt, 100 random points in the unit square.
• uniform_02_00100.png, a PNG image of the data.
• uniform_02_00100.0.05.txt, the points, merged with a tolerance of 0.05.
• uniform_02_00100.0.05.png, a PNG image of the data.
• uniform_02_00100.0.10.txt, the points, merged with a tolerance of 0.10.
• uniform_02_00100.0.10.png, a PNG image of the data.
• uniform_02_00100.0.20.txt, the points, merged with a tolerance of 0.20.
• uniform_02_00100.0.20.png, a PNG image of the data.

List of Routines:

• MAIN is the main program for TABLE_MERGE.
• 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.
• FILE_COLUMN_COUNT counts the number of columns in the first line of a file.
• FILE_NAME_EXT_GET determines the "extension" of a file name.
• FILE_NAME_EXT_SWAP replaces the current "extension" of a file name.
• FILE_ROW_COUNT counts the number of row records in a file.
• GET_UNIT returns a free FORTRAN unit number.
• I4_SWAP switches two integer values.
• I4VEC_HEAP_D reorders an array of integers into a descending heap.
• I4VEC_SORT_HEAP_A ascending sorts an integer array using heap sort.
• NODE_CLUSTER_EPSILON clusters points with a tolerance.
• NODE_MERGE detects nodes that should be merged.
• R8MAT_DATA_READ reads data from an R8MAT file.
• R8MAT_HEADER_READ reads the header from an R8MAT file.
• R8MAT_TRANSPOSE_PRINT prints an R8MAT, transposed.
• R8MAT_TRANSPOSE_PRINT_SOME prints some of an R8MAT, transposed.
• R8MAT_WRITE writes an R8MAT file.
• S_BLANK_DELETE removes blanks from a string, left justifying the remainder.
• S_INDEX_LAST_C finds the LAST occurrence of a given character.
• S_TO_R8 reads an R8 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.

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