VECTOR_PLOT
Plot a 2D Vector Field

VECTOR_PLOT is a FORTRAN90 program which plots a 2D vector field at scattered points.

VECTOR_PLOT reads a file of (X,Y) locations, and a file of (U,V) vector values, and draws a plot of the corresponding vector field (U(X,Y), V(X,Y)), and of the normalized direction field.

VECTOR_PLOT requires the user to specify a "scale factor" for the size of the vectors. A factor of 1.0 is normal, and corresponds to drawing the trail of particles that have traveled for one time unit under the influence of the given velocity. A factor of 0.5 or 2.0 might be used to shorten or lengthen the vectors.

VECTOR_PLOT requires the user to specify a "thinning factor" to discard some of the data. A factor of 1 keeps all the data. A factor of 2 should throw away about every other column and every other row of data (if the (X,Y) coordinates fall on a regular grid.) Thinning the data is a crude but useful tool, because most data files contain far too many vectors to plot.

Usage:

vector_plot xy_file uv_file

• xy_file is a list of the XY coordinates of nodes;
• uv_file is a corresponding list of UV velocity components.

Licensing:

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

Languages:

VECTOR_PLOT is available in a FORTRAN90 version

Related Data and Programs:

BUMP, a FORTRAN90 program which uses the finite element method to study the influence of an obstacle in channel flow. The velocity field can be plotted by VECTOR_PLOT.

CASE1_FLOW, a dataset directory which contains a sequence of velocity vector fields that can be plotted by VECTOR_PLOT.

CAVITY_FLOW, a dataset directory which contains a sequence of velocity vector fields that can be plotted by VECTOR_PLOT.

CHANNEL, a FORTRAN90 program which uses the finite element method to study flow in a channel. The velocity field can be plotted by VECTOR_PLOT.

DIRECTION_ARROWS, a MATLAB program which can plot direction fields.

DIRECTION_ARROWS_GRID, a MATLAB program which reads files of node and velocity data, and, using interpolation, creates a velocity direction plot with arrows place on a uniform grid of the user's specification.

DIRECTION_ARROWS_SEQUENCE, a MATLAB program which can plot a sequence of direction fields for an animation.

DIRECTION_ARROWS_SEQUENCE2, a MATLAB program which can plot a sequence of direction fields for an animation.

DIRECTION_ARROWS2, a MATLAB program which can plot direction fields.

INOUT_FLOW, a dataset directory which contains a sequence of velocity vector fields that can be plotted by VECTOR_PLOT.

INOUT_FLOW2, a dataset directory which contains a sequence of velocity vector fields that can be plotted by VECTOR_PLOT.

MHD_FLOW, a FORTRAN90 program which computes velocity fields which can be plotted by VECTOR_PLOT.

TCELL_FLOW, a dataset directory which contains a sequence of velocity vector fields that can be plotted by VECTOR_PLOT.

VECTOR_MAGNITUDE_GRID, 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.

VECTOR_STREAM_GRID, 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 streamline plot of the vector field.

VELOCITY_ARROWS, a MATLAB program which can plot velocity fields.

VELOCITY_ARROWS_GRID, a MATLAB program which reads files of node and velocity data, and, using interpolation, creates a vector plot with arrows place on a uniform grid of the user's specification.

VELOCITY_ARROWS_GRID2, a MATLAB program which reads a single file of node and velocity data, and using interpolation is able to display a velocity vector field along any uniform grid of points specified by the user.

VELOCITY_ARROWS_SEQUENCE, a MATLAB program which can plot a sequence of velocity fields for an animation.

VELOCITY_ARROWS_SEQUENCE2, a MATLAB program which can plot a sequence of velocity fields for an animation.

VELOCITY_ARROWS2, a MATLAB program which can plot velocity fields.

Source Code:

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

Examples and Tests:

Here is some data from a tcell_flow calculation:

• tcell_xy.txt, the X, Y locations.
• tcell_uv.txt, the U, V velocity component values.
• tcell_dir.png, a PNG image of the velocity direction field, with a thinning factor of 3.
• tcell_vec.png, a PNG image of the vector field, with a thinning factor of 3.

Here is some test data from the MHD_FLOW program. Test files you may copy include:

• mhd_xy.txt, the X, Y locations.
• mhd_uv.txt, the U, V velocity component values.
• mhd_dir.png, a PNG image of the velocity direction field, with a thinning factor of 3.
• mhd_vec.png, a PNG image of the vector field, with a thinning factor of 3.

Here is some spiral test data. Test files you may copy include:

• spiral_xy.txt, the X, Y locations.
• spiral_uv.txt, the U, V velocity component values.
• spiral_dir.png, a PNG image of the velocity direction field.
• spiral_vec.png, a PNG image of the vector field.

List of Routines:

• MAIN is the main program for VECTOR_PLOT.
• BOX_SEGMENT_CLIP_2D uses a box to clip a line segment in 2D.
• CH_CAP capitalizes a single character.
• CH_EQI is a case insensitive comparison of two characters for equality.
• CH_IS_DIGIT returns .TRUE. if a character is a decimal digit.
• CH_TO_DIGIT returns the integer value of a base 10 digit.
• DATA_D2_READ reads a data set of double precision pairs stored in a file.
• DATA_SIZE counts the size of a data set stored in a file.
• DIGIT_TO_CH returns the character representation of a decimal digit.
• DIRECTION_FIELD plots a vector field.
• EPS_FILE_HEAD writes header information to an encapsulated PostScript file.
• EPS_FILE_TAIL writes trailer information to an encapsulated PostScript file.
• FILE_NAME_APPEND appends a string to a filename, before the extension.
• FILE_NAME_EXT_GET determines the "extension" of a file name.
• FILE_NAME_EXT_SWAP replaces the current "extension" of a file name.
• GET_UNIT returns a free FORTRAN unit number.
• I4_SWAP swaps two integer values.
• PS_ARROW draws an arrow from (X1,Y1) to (X2,Y2).
• PS_COLOR_LINE handles the line color.
• PS_COLOR_LINE_SET sets the line color.
• PS_COMMENT inserts a comment into the PostScript file.
• PS_DEFAULT sets the internal settings to their default values
• PS_FILE_CLOSE closes a PostScript file.
• PS_FILE_HEAD writes header information to a PostScript file.
• PS_FILE_OPEN opens a new version of a PostScript file with a given name.
• PS_FILE_TAIL writes trailer information to a PostScript file.
• PS_LINE_CLOSED adds the graph of a closed line to a PostScript file.
• PS_PAGE_HEAD writes header information on a new page.
• PS_PAGE_TAIL writes tail information at the end of a page.
• PS_SETTING_INT sets, gets, or prints integer internal PS_WRITE parameters.
• PS_SETTING_REAL sets, gets, or prints real internal PS_WRITE parameters.
• R8_SWAP swaps two R8's.
• R8VEC_SORT_BUBBLE_A ascending bubble sorts an R8VEC.
• S_EQI is a case insensitive comparison of two strings for equality.
• S_INDEX_LAST finds the LAST occurrence of a given substring.
• S_OF_I4 converts an integer to a left-justified string.
• S_TO_R8 reads an R8 from a string.
• S_WORD_COUNT counts the number of "words" in a string.
• THIN_INDEX determines thinning indices for a X, Y data.
• TIMESTAMP prints the current YMDHMS date as a time stamp.
• TIMESTRING writes the current YMDHMS date into a string.
• VECTOR_FIELD plots a vector field.

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