TRIANGULATION_ORDER3_CONTOUR
Contour Plots of Triangulated Data

TRIANGULATION_ORDER3_CONTOUR is a MATLAB function which reads datafiles describing a set of nodes, their triangulation, and the value of a scalar quantity at each node, and creates a color contour plot of the scalar.

The program reads three data files:

• node_file, containing X, Y coordinates of points;
• element_file, containing a list of sets of three points making up each triangular element;
• solution_file, containing the value of a scalar function U(X,Y) evaluated at each node.

The program automatically displays three plots:

1. An image of the triangulation;
2. A color contour plot with color constant over a triangle.
3. A color contour plot with color linearly interpolated to make a very nice picture.

Usage:

triangulation_order3_contour ( node_file, element_file, solution_file )

runs the program, using the given node, element and solution files.

Related Data and Programs:

FEM is a data directory which contains a description and examples of the FEM format.

FEM_BASIS_T3_DISPLAY is a MATLAB program which displays a basis function associated with a linear triangle ("T3") mesh.

FREE_FEM_STOKES is an executable MATLAB program which is a Stokes flow solver which computes the fluid velocity and pressure in a 2D region. The pressure is a scalar, an order 3 triangulation is used for the pressure, and so it can be plotted by this routine.

TABLE is the format used for each of the three input data files.

TRIANGULATION is a MATLAB library of routines for carrying out various operations on order 3 ("linear") or order 6 ("quadratic") triangulations.

TRIANGULATION_MASK is an executable MATLAB program, which takes an existing triangulation and deletes triangles and their corresponding nodes as requested by the user.

TRIANGULATION_ORDER3 is a directory which describes the format for the node and element files describing an order 3 triangulation.

TRIANGULATION_ORDER6_CONTOUR is an executable MATLAB program which can display a contour plot of scalar data defined on a triangulation of order 6.

TRIANGULATION_ORIENT is an executable MATLAB program that reads data defining a triangulation, makes sure that every triangle has positive orientation, and if not, writes a corrected triangle file.

TRIANGULATION_REFINE is an executable MATLAB program that reads data defining a triangulation, replaces each triangle by four congruent smaller ones, and writes the new triangulation information to a file.

VECTOR_MAGNITUDE_GRID is a MATLAB program which reads node and vector data from a file, computes an interpolatory function, evaluates on a uniform grid of points specified by the user, and displays a contour plot of the vector magnitude.

Source Code:

• triangulation_order3_contour.m, the routine for creating the contour plot;
• timestamp.m, prints the current YMDHMS date as a timestamp;

Examples and Tests:

CHANNEL is a channel region 3 units wide and 1 unit high. The Stokes flow solver FREE_FEM_STOKES computes the fluid velocity and pressure in the channel. The pressure is a scalar and can be plotted by this routine. Data files you can copy include:

• channel_nodes.txt, a node file;
• channel_triangles.txt, an element file;
• channel_pressure.txt, a solution file;
• channel_pressure.png, a PNG image of the interpolated contour plot of the data;

ELL is an L-shaped region. Data files you can copy include:

• ell_nodes.txt, a node file;
• ell_elements.txt, an element file;
• ell_solution.txt, a solution file;
• ell_triangulation.png, a PNG image of the triangulation;
• ell_pw_constant.png, a PNG image of the piecewise constant contour plot of the data;
• ell_interp.png, a PNG image of the interpolated contour plot of the data;

LAKE is a simulated lake with an island region. Data files you can copy include:

• lake_nodes.txt, a node file;
• lake_elements.txt, an element file;
• lake_solution.txt, a solution file;
• lake_triangulation.png, a PNG image of the triangulation;
• lake_pw_constant.png, a PNG image of the piecewise constant contour plot of the data;
• lake_interp.png, a PNG image of the interpolated contour plot of the data;

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