PLINTH
Piecewise Linear Interpolation, Hierarchical

PLINTH is a MATLAB library which carries out tasks associated with the interpolation of data or a function by a hierarchical set of piecewise linear functions.

Licensing:

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

Languages:

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

Related Data and Programs:

DIVDIF, a MATLAB library which computes divided difference polynomials from data;

INTERP, a FORTRAN90 library which can be used for parameterizing and interpolating data;

PPPACK, a FORTRAN90 library which defines piecewise polynomial functions, including, in particular, cubic splines.

SPINTERP, a MATLAB library which carries out piecewise multilinear hierarchical sparse grid interpolation; an earlier version of this software is ACM TOMS Algorithm 847, by Andreas Klimke;

SPLINE, a MATLAB library which includes many routines to construct and evaluate spline interpolants and approximants.

TEST_APPROX, a MATLAB library which defines a number of test problems for approximation and interpolation.

TOMS847, a MATLAB library which carries out piecewise multilinear hierarchical sparse grid interpolation; this library is commonly called SPINTERP (version 2.1); this is ACM TOMS Algorithm 847, by Andreas Klimke;

Source Code:

• r8btree_bracket.m, finds X1 <= X <= X2 from a BTREE.
• r8btree_bracket_level.m, finds X1 <= X <= X2 from a BTREE, limiting the search depth to no more than a given level.
• r8btree_interp.m, interpolates data in the BTREE.
• r8btree_interp_level.m, interpolates data in the BTREE, limiting the search depth to no more than a given level. This results in a hierarchical family of interpolants.
• r8btree_node_add.m, adds one node to a BTREE.
• r8btree_print.m, prints a BTREE.
• r8btree_print_ordered.m, prints the nodes of a BTREE in order.
• timestamp.m, prints the current YMDHMS date as a time stamp.

Examples and Tests:

• p77_fun.m, a "wiggly" function used for interpolation tests.
• r8btree_bracket_test.m, tests R8BTREE_BRACKET.
• r8btree_bracket_test_output.txt, output from R8BTREE_BRACKET_TEST.
• r8btree_bracket_level_test.m, tests R8BTREE_BRACKET_LEVEL.
• r8btree_bracket_level_test_output.txt, output from R8BTREE_BRACKET_LEVEL_TEST.
• r8btree_interp_test.m, tests R8BTREE_INTERP.
• r8btree_interp_test_output.txt, output from R8BTREE_INTERP_TEST.
• r8btree_interp_level_test.m, tests R8BTREE_INTERP_LEVEL.
• r8btree_interp_level_test_output.txt, output from R8BTREE_INTERP_LEVEL_TEST.
• p77_fun.png a plot of the wiggly function P77 over [-0.5,2.5],.
• p77_fun_level0.png a plot, over [-0.5,2.5], of a level 0 interpolant to P77 over [0,2].
• p77_fun_level1.png a plot, over [-0.5,2.5], of a level 1 interpolant to P77 over [0,2].
• p77_fun_level2.png a plot, over [-0.5,2.5], of a level 2 interpolant to P77 over [0,2].
• p77_fun_level3.png a plot, over [-0.5,2.5], of a level 3 interpolant to P77 over [0,2].
• p77_fun_level4.png a plot, over [-0.5,2.5], of a level 4 interpolant to P77 over [0,2].
• p77_fun_level5.png a plot, over [-0.5,2.5], of a level 5 interpolant to P77 over [0,2].
• r8btree_node_add_binary_test.m, adds binary fractions to a BTREE.
• r8btree_node_add_binary_test_output.txt, output from R8BTREE_NODE_ADD_BINARY_TEST.
• r8btree_node_add_random_test.m, adds random numbers to a BTREE.
• r8btree_node_add_random_test_output.txt, output from R8BTREE_NODE_ADD_RANDOM_TEST.
• r8btree_print_ordered_test.m, tests R8BTREE_PRINT_ORDERED.
• r8btree_print_ordered_test_output.txt, output from R8BTREE_PRINT_ORDERED_TEST.
• r8btree_print_test.m, tests R8BTREE_PRINT.
• r8btree_print_test_output.txt, output from R8BTREE_PRINT_TEST.

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