vector_plot/vector_plot.html

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      VECTOR_PLOT - Plot a 2D Vector Field
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    <h1 align = "center">
      VECTOR_PLOT <br> Plot a 2D Vector Field
    </h1>

    <hr>

    <p>
      <b>VECTOR_PLOT</b>
      is a FORTRAN90 program which
      plots a 2D vector field at scattered points.
    </p>

    <p>
      <b>VECTOR_PLOT</b> 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.
    </p>

    <p>
      <b>VECTOR_PLOT</b> 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.
    </p>

    <p>
      <b>VECTOR_PLOT</b> 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.
    </p>

    <h3 align = "center">
      Usage:
    </h3>

    <p>
      <blockquote>
        <b>vector_plot</b> <i>xy_file</i> <i>uv_file</i>
      </blockquote>
      where
      <ul>
        <li>
          <i>xy_file</i> is a list of the XY coordinates of nodes;
        </li>
        <li>
         <i>uv_file</i> is a corresponding list of UV velocity components.
        </li>
      </ul>
    </p>

    <h3 align = "center">
      Licensing:
    </h3>

    <p>
      The computer code and data files described and made available on this web page
      are distributed under
      <a href = "../../txt/gnu_lgpl.txt">the GNU LGPL license.</a>
    </p>

    <h3 align = "center">
      Related Data and Programs:
    </h3>

    <p>
      <a href = "../../f_src/bump/bump.html">
      BUMP</a>,
      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 <b>VECTOR_PLOT</b>.
    </p>

    <p>
      <a href = "../../datasets/case1_flow/case1_flow.html">
      CASE1_FLOW</a>,
      a dataset directory which
      contains a sequence of
      velocity vector fields that can be plotted by <b>VECTOR_PLOT</b>.
    </p>

    <p>
      <a href = "../../datasets/cavity_flow/cavity_flow.html">
      CAVITY_FLOW</a>,
      a dataset directory which
      contains a sequence of
      velocity vector fields that can be plotted by <b>VECTOR_PLOT</b>.
    </p>

    <p>
      <a href = "../../f_src/channel/channel.html">
      CHANNEL</a>,
      a FORTRAN90 program which
      uses the finite element method
      to study flow in a channel.  The velocity field can be plotted by
      <b>VECTOR_PLOT</b>.
    </p>

    <p>
      <a href = "../../m_src/direction_arrows/direction_arrows.html">
      DIRECTION_ARROWS</a>,
      a MATLAB program which
      can plot direction
      fields.
    </p>

    <p>
      <a href = "../../m_src/direction_arrows_grid/direction_arrows_grid.html">
      DIRECTION_ARROWS_GRID</a>,
      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.
    </p>

    <p>
      <a href = "../../m_src/direction_arrows_sequence/direction_arrows_sequence.html">
      DIRECTION_ARROWS_SEQUENCE</a>,
      a MATLAB program which
      can plot
      a sequence of direction fields for an animation.
    </p>

    <p>
      <a href = "../../m_src/direction_arrows_sequence2/direction_arrows_sequence2.html">
      DIRECTION_ARROWS_SEQUENCE2</a>,
      a MATLAB program which
      can plot
      a sequence of direction fields for an animation.
    </p>

    <p>
      <a href = "../../m_src/direction_arrows2/direction_arrows2.html">
      DIRECTION_ARROWS2</a>,
      a MATLAB program which
      can plot direction
      fields.
    </p>

    <p>
      <a href = "../../datasets/inout_flow/inout_flow.html">
      INOUT_FLOW</a>,
      a dataset directory which
      contains a sequence of
      velocity vector fields that can be plotted by <b>VECTOR_PLOT</b>.
    </p>

    <p>
      <a href = "../../datasets/inout_flow2/inout_flow2.html">
      INOUT_FLOW2</a>,
      a dataset directory which
      contains a sequence of
      velocity vector fields that can be plotted by <b>VECTOR_PLOT</b>.
    </p>

    <p>
      <a href = "../../f_src/mhd_flow/mhd_flow.html">
      MHD_FLOW</a>,
      a FORTRAN90 program which
      computes velocity fields
      which can be plotted by <b>VECTOR_PLOT</b>.
    </p>

    <p>
      <a href = "../../datasets/tcell_flow/tcell_flow.html">
      TCELL_FLOW</a>,
      a dataset directory which
      contains a sequence of
      velocity vector fields that can be plotted by <b>VECTOR_PLOT</b>.
    </p>

    <p>
      <a href = "../../m_src/vector_magnitude_grid/vector_magnitude_grid.html">
      VECTOR_MAGNITUDE_GRID</a>,
      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.
    </p>

    <p>
      <a href = "../../m_src/vector_stream_grid/vector_stream_grid.html">
      VECTOR_STREAM_GRID</a>,
      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.
    </p>

    <p>
      <a href = "../../m_src/velocity_arrows/velocity_arrows.html">
      VELOCITY_ARROWS</a>,
      a MATLAB program which
      can plot velocity
      fields.
    </p>

    <p>
      <a href = "../../m_src/velocity_arrows_grid/velocity_arrows_grid.html">
      VELOCITY_ARROWS_GRID</a>,
      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.
    </p>

    <p>
      <a href = "../../m_src/velocity_arrows_grid2/velocity_arrows_grid2.html">
      VELOCITY_ARROWS_GRID2</a>,
      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.
    </p>

    <p>
      <a href = "../../m_src/velocity_arrows_sequence/velocity_arrows_sequence.html">
      VELOCITY_ARROWS_SEQUENCE</a>,
      a MATLAB program which
      can plot
      a sequence of velocity fields for an animation.
    </p>

    <p>
      <a href = "../../m_src/velocity_arrows_sequence2/velocity_arrows_sequence2.html">
      VELOCITY_ARROWS_SEQUENCE2</a>,
      a MATLAB program which
      can plot
      a sequence of velocity fields for an animation.
    </p>

    <p>
      <a href = "../../m_src/velocity_arrows2/velocity_arrows2.html">
      VELOCITY_ARROWS2</a>,
      a MATLAB program which
      can plot velocity fields.
    </p>

    <h3 align = "center">
      Source Code:
    </h3>

    <p>
      <ul>
        <li>
          <a href = "vector_plot.f90">vector_plot.f90</a>, the source code.
        </li>
        <li>
          <a href = "vector_plot.sh">vector_plot.sh</a>,
          commands to compile the source code.
        </li>
      </ul>
    </p>

    <h3 align = "center">
      Examples and Tests:
    </h3>

    <p>
      Here is some data from a
      <a href = "../../datasets/tcell_flow/tcell_flow.html">
      tcell_flow</a> calculation:
      <ul>
        <li>
          <a href = "tcell_xy.txt">tcell_xy.txt</a>,
          the X, Y locations.
        </li>
        <li>
          <a href = "tcell_uv.txt">tcell_uv.txt</a>,
          the U, V velocity component values.
        </li>
        <li>
          <a href = "tcell_dir.png">
          tcell_dir.png</a>,
          a <a href = "../../data/png/png.html">PNG</a>
          image of the velocity direction field,
          with a thinning factor of 3.
        </li>
        <li>
          <a href = "tcell_vec.png">
          tcell_vec.png</a>,
          a <a href = "../../data/png/png.html">PNG</a>
          image of the vector field,
          with a thinning factor of 3.
        </li>
      </ul>
    </p>

    <p>
      Here is some test data from the
      <a href = "../../f_src/mhd_flow/mhd_flow.html">MHD_FLOW</a> program.
      Test files you may copy include:
      <ul>
        <li>
          <a href = "mhd_xy.txt">mhd_xy.txt</a>,
          the X, Y locations.
        </li>
        <li>
          <a href = "mhd_uv.txt">mhd_uv.txt</a>,
          the U, V velocity component values.
        </li>
        <li>
          <a href = "mhd_dir.png">
          mhd_dir.png</a>,
          a <a href = "../../data/png/png.html">PNG</a>
          image of the velocity direction field,
          with a thinning factor of 3.
        </li>
        <li>
          <a href = "mhd_vec.png">
          mhd_vec.png</a>,
          a <a href = "../../data/png/png.html">PNG</a>
          image of the vector field,
          with a thinning factor of 3.
        </li>
      </ul>
    </p>

    <p>
      Here is some spiral test data.
      Test files you may copy include:
      <ul>
        <li>
          <a href = "spiral_xy.txt">spiral_xy.txt</a>,
          the X, Y locations.
        </li>
        <li>
          <a href = "spiral_uv.txt">spiral_uv.txt</a>,
          the U, V velocity component values.
        </li>
        <li>
          <a href = "spiral_dir.png">
          spiral_dir.png</a>,
          a <a href = "../../data/png/png.html">PNG</a>
          image of the velocity direction field.
        </li>
        <li>
          <a href = "spiral_vec.png">
          spiral_vec.png</a>,
          a <a href = "../../data/png/png.html">PNG</a>
          image of the vector field.
        </li>
      </ul>
    </p>

    <h3 align = "center">
      List of Routines:
    </h3>

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

    <p>
      You can go up one level to <a href = "../f_src.html">
      the FORTRAN90 source codes</a>.
    </p>

    <hr>

    <i>
      Last revised on 15 November 2006.
    </i>

    <!-- John Burkardt -->

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