TRIANGULATION_NODE_TO_ELEMENT
Average Node Data to Create Element Data

TRIANGULATION_NODE_TO_ELEMENT is a C++ program which reads datafiles describing a set of nodes, their triangulation, and the value of one or more quantities at each node, and outputs a file that averages the quantities for each element. This operation in effect creates an "order1" finite element model of the data.

The program reads three data files:

• a node file, containing X, Y coordinates of points;
• an element file, containing a list of sets of three points making up each triangular element; (if this file does not exist, the program will generate the element data automatically).
• a node values file, containing the values of one or more data items at each node.

• an element values file, containing the values of the data, averaged over the nodes in each element.

Usage:

triangulation_node_to_element prefix

• prefix_nodes.txt, lists the node coordinates;
• prefix_elements.txt lists the indices of nodes that form elements (this file is optional, and if not supplied, the information will be generated internally);
• prefix_values.txt contains the value assigned to each node.
• prefix_element_values.txt will contain the values averaged over the nodes in each element.

Licensing:

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

Languages:

TRIANGULATION_NODE_TO_ELEMENT is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

TRIANGULATION, a C++ library which carries out various operations on order 3 ("linear") or order 6 ("quadratic") triangulations.

TRIANGULATION_L2Q, a C++ program which reads information about a 3-node (linear) triangulation and creates data defining a corresponding 6-node (quadratic) triangulation;

TRIANGULATION_Q2L, a C++ program which reads information about a 6-node (quadratic) triangulation and creates data defining a corresponding 3-node (linear) triangulation;

Source Code:

• triangulation_node_to_element.cpp, the source code.
• triangulation_node_to_element.sh, BASH commands to compile the source code.

Examples and Tests:

• lake_nodes.txt, the node coordinate file.
• lake_elements.txt, the element file.
• lake_values.txt, the node values file.
• lake_element_values.txt, the element_values file created by the program.

List of Routines:

• MAIN is the main program for TRIANGULATION_NODE_TO_ELEMENT.
• 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_ROW_COUNT counts the number of row records in a file.
• I4MAT_DATA_READ reads data from an I4MAT file.
• I4MAT_HEADER_READ reads the header from an I4MAT.
• I4MAT_TRANSPOSE_PRINT_SOME prints some of the transpose of an I4MAT.
• I4MAT_WRITE writes an I4MAT file.
• MESH_BASE_ONE ensures that the element definition is one-based.
• R8MAT_DATA_READ reads data from an R8MAT file.
• R8MAT_HEADER_READ reads the header from an R8MAT file.
• R8MAT_TRANSPOSE_PRINT_SOME prints some of an R8MAT, transposed.
• R8MAT_WRITE writes an R8MAT file.
• S_TO_I4 reads an I4 from a string.
• S_TO_I4VEC reads an I4VEC from a string.
• 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 C++ source codes.