%  @(#)plot_vect.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:43:49
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      plot_vect.hlq
%.AUTHOR     RHW, IPG/ESO
%.KEYWORDS   MIDAS, help files, PLOT/VECTOR
%.PURPOSE    On-line help file for the command: PLOT/VECTOR
%.VERSION    900812 RHW Implementation
%----------------------------------------------------------------
\se
SECTION./VECT
\es\co
PLOT/VECTOR                                                     26-AUG-1991 RHW
\oc\su
PLOT/VECTOR frame_a frame_b [coord_str] [x_sc,y_sc[,x_off,y_off]] [scale_r] 
            [range] [sm_par] [head]
	plot vector map from two 2-dim. images with smoothing option
\us\pu
Purpose: 
             Plot vector map from two 2-dim. images with smoothing option
\up\sy
Syntax:
             PLOT/VECTOR frame_a frame_b [coord_str] [x_sc,y_sc[,x_off,y_off]]
                         [scale_r] [range] [sm_par] [head]
\ys\pa
             frame_a =   input frame containing the intensities
\ap\pa
             frame_b =   input frame containing the position angles
\ap\pa
             coord_str = area to be plotted in standard MIDAS notation; see 
                         MIDAS Users Guide Chapter 3. Default is either any 
                         manual setting done with by the SET/GRAPHICS command, 
                         or the whole area.
\ap\pa
             x_sc,y_sc,x_off,y_off = scale or size in the x- and y-direction,
                         offset in the x- and y-direction. For the scaling x_sc
                         and y_sc, positive numbers are interpreted as scale
                         parameters (world units/mm), negative numbers as size
                         parameters (axis will be made sc_* mm. long). A
                         combination of a positive and negative number is
                         allowed. By default the plot fills the device area. \\
                         x_off and y_off determine the distance of the lower
                         left corner of the plot to the lower left corner of 
                         the graphic device, measured in mm. By default, the 
                         plot is put at the top left of the graphic device, 
                         allowing space for the various labels.
\ap\pa
             scale_r =   scale of the vector length in intensity units/mm. By
                         default the command computes the average of the 
                         minimimum and maximum cut values in the descriptor of
                         frame_a; this average intensity will correspond to a
                         vector length of 10 mm.
\ap\pa
             range =     intensity and position angle (in degrees) ranges to 
                         be plotted. Default is all vectors (i.e. 0,0,0,360 =
                         all intensities and all position angles). The position
                         angle is defined using the standard astronomical 
                         convention: 0 is pointing to the top, and the angle 
                         increases counter-clockwise. For the length of the 
                         vector the absolute values of the pixels in the 
                         intensity image is taken; The postion angles are 
                         assumed positive.
\ap\pa
             sm_par    = smoothing parameter i.e. the number of pixels "around"
                         the central pixel which define the neighbourhood of
                         that pixel. \\
                         Total number of pixels is then: (2*sm_par + 1)**2 
                         Only integer numbers are allowed. Default is 0
\ap\pa
             head      = integer number. If the vector should have an arrow at
                         its end this parameter should be 1, else give a 0.
                         Default is 1, i.e. the arrow is drawn.
\ap\no
Note:        
             The coordinates for the area are optional. If one specifies a "?",
             the area will be take for the manual frame settings for the x-
             and y-axis. If "C" is given, the window is selected interactively
             on the display screen using the cursor facilities. The cursor will
             be set on automatically, if it is not already. To pick up the
             coordinates, switch the cursors ON and press ENTER. To exit,
             switch the cursors OFF and press ENTER.
\on\see
See also:
             OVERPLOT/VECTOR, SHOW/GRAPHICS, SET/GRAPHICS, PLOT/AXES, 
             PLOT/CONTOUR, OVERPLOT/CONTOUR, PLOT/GRAY, OVERPLOT/GRAY
\ees\exs
Examples:
\ex
             PLOT/VECT spir_i spir_p [@281,@281:@320,@320] ? 0.5 ? 1
             Plot the polarisation vector using the intensities from spir_i
             and the position angle information form spir_p. Use the default
             scale for the axes, and a scale of 0.5 units/mm for the size of
             the vectors (i.e. an intensity of 10 pixel units will make the
             vector 20 mm). Apply a box smoothing over 3x3 pixels.
\xe \sxe