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DCL:GRPH2:UGPACK :Vector Field Display Routines

10.1 Summary

The UGPACK is a subroutine package for drawing 2-D vector fields. At the present, processes such as the scaling of vector length are performed in the V-coordinate and the vector is drawn in the V-coordinate, so this package can only be used for Cartesian linear coordinates (transformation function numbers ITR = 1-4).

In this package, a vector is drawn using the arrow sub-primitives of GRPH1. This package only draws a vector field, and does not draw the outer frames such as the coordinate axes.

Below are the subroutines a user will be using in the UGPACK.

• Draw Routine

  UGVECT . . . Draws a 2-D vector field.

• Other Routines

  UGSUT . . . Sets the title of a unit vector.

  UGpGET/UGpSET. . . Inquires/changes an internal variable.

Information concerning the grid- point coordinates are handled by UWPACK. (See Chapter 11.)

• Routines for Setting the Grid-Point Coordinates

  UWSGXA/UWSGYA . . . Sets each grid-point by giving the coordinate value.

  UWSGXB/UWSGYB . . . Sets by minimum and maximum values.

When you want a quick look of the vector data given on 2-D grid points, simply call UGVECT. When this call is made, evenly-spaced grid points are set to fill the whole area of the current window, and the scaling of vector lengths will be performed automatically.

If the grid points are not evenly spaced, specify the coordinate values of the grid points by calling UWSGXA (X direction)/ UWSGYA  (Y-direction) before calling UGVECT. Or, when you wish to set evenly-spaced grid points in only a part of the window, specify the minimum and maximum value of the gird points using UWSGXB (X direction)/ UWSGYB   (Y-direction).

You may also specify the internal variables to change the scaling factor or to draw a unit vector. (An "internal variable" refers to an internal variable that is handled by UGpGET/UGpSET, unless specified otherwise.)