DISK_GRID
Grid Points Within a Disk

DISK_GRID is a FORTRAN90 library which generates a grid of points over the interior of a disk in 2D.

The library allows the user to define an arbitrary disk by choosing its radius and center. The user also chooses N, the number of subintervals into which the horizontal radius line will be subdivided. It then returns the gridpoints defined by that choice.

Another function allows the user to specify that N points on a Fibonacci spiral are to be placed within the disk.

The test program creates input files to GNUPLOT which will create graphic images of the grids.

Licensing:

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

Languages:

DISK_GRID is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version and a Python version.

Related Data and Programs:

BALL_GRID, a FORTRAN90 library which computes a grid of points over the interior of a ball in 3D.

CIRCLE_ARC_GRID, a FORTRAN90 program which computes points equally spaced along a circular arc;

CUBE_GRID, a FORTRAN90 library which computes a grid of points over the interior of a cube in 3D.

ELLIPSE_GRID, a FORTRAN90 library which computes a grid of points over the interior of an ellipse in 2D.

ELLIPSOID_GRID, a FORTRAN90 library which computes a grid of points over the interior of an ellipsoid in 3D.

GNUPLOT, FORTRAN90 programs which illustrate how a program can write data and command files so that gnuplot can create plots of the program results.

HYPERCUBE_GRID, a FORTRAN90 library which computes a grid of points over the interior of a hypercube in M dimensions.

LINE_GRID, a FORTRAN90 library which computes a grid of points over the interior of a line segment in 1D.

POLYGON_GRID, a FORTRAN90 library which generates a grid of points over the interior of a polygon in 2D.

PYRAMID_GRID, a FORTRAN90 library which computes a grid of points over the interior of the unit pyramid in 3D;

SIMPLEX_GRID, a FORTRAN90 library which generates a grid of points over the interior of a simplex in M dimensions.

SPHERE_CUBED_GRID, a FORTRAN90 library which uses the projection of a cube to create grids of points, lines, and quadrilaterals on the surface of the unit sphere in 3D.

SPHERE_FIBONACCI_GRID, a FORTRAN90 library which uses a Fibonacci spiral to create a grid of points on the surface of the unit sphere in 3D.

SPHERE_GRID, a FORTRAN90 library which provides a number of ways of generating grids of points, or of points and lines, or of points and lines and faces, on the surface of the unit sphere in 3D.

SPHERE_LLQ_GRID, a FORTRAN90 library which uses longitudes and latitudes to create grids of points, lines, and quadrilaterals on the surface of the unit sphere in 3D.

SPHERE_LLT_GRID, a FORTRAN90 library which uses longitudes and latitudes to create grids of points, lines, and triangles on the surface of the unit sphere in 3D.

TETRAHEDRON_GRID, a FORTRAN90 library which computes a grid of points over the interior of a tetrahedron in 3D.

TRIANGLE_GRID, a FORTRAN90 library which computes a grid of points over the interior of a triangle in 2D.

WEDGE_GRID, a FORTRAN90 library which computes a grid of points over the interior of the unit wedge in 3D.

Reference:

1. Richard Swinbank, James Purser,
   Fibonacci grids: A novel approach to global modelling,
   Quarterly Journal of the Royal Meteorological Society,
   Volume 132, Number 619, July 2006 Part B, pages 1769-1793.

Source Code:

• disk_grid.f90, the source code.

Examples and Tests:

• disk_grid_test.f90, a sample calling program.
• disk_grid_test.txt, the output file.
• disk_grid_test01.xy, the list of grid points.
• disk_grid_test01_boundary.txt, coordinates of the bounding circle.
• disk_grid_test01_data.txt, coordinates of the grid points.
• disk_grid_test01_commands.txt, input commands to Gnuplot to create an image.
• disk_grid_test01.png, an image of the points.
• disk_grid_test02.xy, the list of Fibonacci grid points.
• disk_grid_test02_boundary.txt, coordinates of the bounding circle.
• disk_grid_test02_data.txt, coordinates of the grid points.
• disk_grid_test02_commands.txt, input commands to Gnuplot to create an image.
• disk_grid_test02.png, an image of the points.

List of Routines:

• DISK_GRID computes grid points inside a disk.
• DISK_GRID_COUNT counts the grid points inside a disk.
• DISK_GRID_FIBONACCI computes Fibonacci grid points inside a disk.
• GET_UNIT returns a free FORTRAN unit number.
• R82VEC_PRINT_PART prints "part" of an R82VEC.
• R8MAT_WRITE writes an R8MAT file.
• TIMESTAMP prints the current YMDHMS date as a time stamp.

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