functions in plot.i -

             __pl_color_list - private list of color names  
 

             __plp, x, y;  
 
     Private routine used by plp. */  

             _pl3tick, p, d, v  
 
     draw axis between (P(1),P(2),P(3)) and ((P+D)(1),(P+D)(2),(P+D)(3))  
     and ticks with vectorial length (V(1),V(2),V(3)).  

             _pl3xy, xp, yp, x, y, z  
 
     transform data coordinates (X,Y,Z) into viewer coordinates  
     (XP,YP) for an externally defined altitude ALT and  
     azimuth AZ (in degrees).  

             _pl3xyz, xp, yp, zp, x, y, z  
 
     transform data coordinates (X,Y,Z) into viewer coordinates  
     (XP,YP,ZP) for an externally defined altitude ALT and  
     azimuth AZ (in degrees).  

             color_bar;  
          or color_bar, levs, colors;  
 
     Draw a color bar below the  current coordinate system.  If LEVS is not  
     specified uses plfc_levs (set by previous call to plfc).  If COLORS is  
     specified, it should have one  more value than LEVS, otherwise equally  
     spaced colors are chosen, or  plfc_colors if plfc_levs was used.  With  
     the VERT=1  keyword the color bar  appears to the left  of the current  
     coordinate  system (vert=0  is default).   By default,  color_bar will  
     attempt  to  label some  of  the  color  interfaces.  With  the  LABS  
     keyword,  you can  force the  labelling algorithm  as  follows: LABS=0  
     supresses all  labels, LABS=n forces  a label at every  n-th interface,  
     LABS=[i,n]  forces  a  label  at  every n-th  interface  starting  from  
     interface i (0<=i<=numberof(LEVS)).  
     You    can    specify   the    viewport    coordinates   by    keyword  
     VPORT=[xmin,xmax,ymin,ymax]; by default the  colorbar is drawn next to  
     the current viewport.  You can use the ADJUST keyword  to move the bar  
     closer to (adjust<0) or further from (adjust>0) the viewport.  
     You  can specify  the string  format  for labels  with keyword  FORMAT  
     (default "%g"), the font  type with keyword FONT (default "helvetica")  
     and the font height with keyword HEIGHT (default 14 points).  
     Keyword COLOR  can be  used to  specify the color  of the  labels, the  
     ticks and the frame of the colorbar.  Default is foreground color.  
     Keyword WIDTH can be  used to set the width of the  lines used to draw  
     the frame and the ticks of the colorbar.  
     Keyword TICKLEN  can be used to set  the lenght (in NDC  units) of the  
     ticks.  Default is 0.005 NDC.  
       

             pl3dj, x0, y0, z0, x1, y1, z1, alt=alt, az=az  
 
     plots disjoint lines from (X0,Y0,Z0) to (X1,Y1,Z1) in a 3-dimensional  
     graph view from altitude ALT (default 45) and azimuth AZ (default 30)  
     both in degrees.  X0, Y0, Z0, X1, Y1 and Z1 must have the same shapes.  
     Additional keywords are those accepted by pldj: legend, hide, type,  
     width, and color.  

             pl3s, z, y, x, fill=0/1/2  
          or pl3s, z, fill=0/1/2  
 
      draws 3-D surface plot of Z versus (X,Y).   The  Z  array  must  be a  
      2-dimensional array, say NX-by-NY and X  and  Y  must  have  the same  
      shape as Z or be vectors  of  length  NX  and  NY  respectively.   If  
      omitted, X and Y are set to the first and second  indice  value  of Z  
      respectively.  
      The FILL keyword indicates the kind of plot: 0 (default) for  3D wire  
      frames, 1 for 3D mesh filled with intensity,  2  for  3D  mesh shaded  
      with light source aligned with observer.  
      The altitude and azimuth angles (in degrees) can be set with keywords  
      ALT and AZ, their default values are 30 and 45 deg.  
      A solid edge can optionally be drawn around each zone by  setting the  
      EDGES keyword non-zero.  ECOLOR and EWIDTH determine  the  edge color  
      and width.  
      Frame axis can optionally be drawn around  the  plot  by  setting the  
      AXIS keyword non-zero.  The  color  of  the  axis  and  label  can be  
      modified with keyword ACOLOR.  
      If BOX keyword non-zero, the 3-D box borders are drawn (with the same  
      color as the axis, i.e., ACOLOR).  
   EXAMPLE  
     It is usually better to select an eventually new window and choose  
     the "nobox" style:  
       window, max(0, current_window()), wait=1, style="nobox.gs";  
       x= span(-3,3,50);  
       y= span(-2,2,40);  
       z= cos(x(,-) * y(-,));  
       pl3s, z, y, x, axis=1, fill=2, edges=1, font="timesBI", height=10;  
      The following keywords are legal (each has a separate help entry):  
   KEYWORDS: legend, hide, region, edges, ecolor, ewidth, font, height.  

             pl3t, text, x, y, z, alt=alt, az=az, tosys=0/1  
 
     plots TEXT (a string) at the point (X,Y,Z) in a 3-dimensional  
     graph view from altitude ALT (default 45) and azimuth AZ  
     (default 30) both in degrees.   TEXT, X, Y and Z may be arrays  
     with the same number of elements.  
     Other optional keywords are:  
       legend, hide, color, font, height, opaque, path, justify and tosys  
     and have the same meaning as in plt.  

             pla, y, x  
          or pla, y  
 
	Plot the  buddle of curves Y versus X labelled by the last indice.  
	Y must be 2-dimensional, and X may be 2-dimensional, 1-dimensional  
	or omitted.  If X is 2-dimensional, it must have the same dimensions  
	as Y and Y(,i) versus X(,i) is plotted for each last indice i.  If  
	X is 1-dimensional, it must have the same length as the 1st dimension  
	of Y and Y(,i) versus X is plotted for each last indice i.  If X is  
	omitted, it defaults to [1, 2, ..., numberof(Y(,1))].  
	The plotting keywords of plg are accepted plus the optional keyword  
	every=N which can be used to plot every N curves in the bundle  
	(default N=1).  
   EXAMPLE  
	x =span(0,1,25)(,-:1:25);  
	pla, x*transpose(x), marks=0, every=3;  

             plh, y, x  
          or plh, y  
 
	plots a graph of Y versus X in an "histogram" style (i.e., with  
	steps).  Y and X must be 1-D arrays of equal length; if X is  
	omitted, it defaults to [1, 2, ..., numberof(Y)].  
	The optional keyword JUST set justification of the histogram:  
	JUST=1, 2 or 3 makes the graph be left justified, centered or  
	right justified respectively along X axis.  Default is centered.  
	Other plotting keywords (legend, hide, type, width, color, marks,  
	marker, mspace, and mphase) are passed to the plg routine.  

             plhline, y;  
 
       -or- plhline, y, x0, x1;  
       -or- plvline, x;  
       -or- plhline, x, y0, y1;  
     Plots an horizontal/vertical line.  
   KEYWORDS color, type, width.  

             plp, y, x  
 
       -or- plp, y, x, dx=sigma_x, dy=sigma_y  
     Plots points (X,Y) with symbols and/or  error bars.  X, and Y may have  
     any dimensionality, but  must have the same number  of elements.  If X  
     is nil, it defaults to indgen(numberof(Y)).  
     Keyword SYMBOL may be used to choose the shape of each symbol:  
       0    nothing (just draw error bars if any)  
       1    square  
       2    cross (+ sign)  
       3    triangle  
       4    circle (hexagon)  
       5    diamond  
       6    cross (rotated 45 degrees)   <- this is the default  
       7    triangle (upside down)  
       8    star  
     >=9    SYMBOL-side polygon  
     Keyword  SIZE may be used to  change the size of the  symbols and tick  
     marks (SIZE acts as a multiplier, default value is 1.0).  
     If value of  keyword FILL is true (non-nil  and non-zero), symbols are  
     filled with COLOR (default is to draw open symbols).  
     Keywords XLO, XHI, YLO, and/or YHI  can be used to indicate the bounds  
     of the optional  error bars (default is to draw  no error bars).  Only  
     specified bounds get plotted as  error bars. If value of keyword TICKS  
     is true  (non-nil and non-zero), ticks  get drawn at  the endpoints of  
     the error bars.   Alternatively, keywords DX and/or DY  can be used to  
     plot  error bars  as segments  from XLO=X-DX  to XHI=X+DX  and/or from  
     YLO=Y-DY to  YHI=Y+DY.  If keyword  DX (respectively DY) is  used, any  
     value of XLO and XHI (respectively YLO and YHI) is ignored.  
     The other keywords are the same as for pldj (TYPE is only used to draw  
     error bars):  
   KEYWORDS: legend, type, width, color.  

             pls, z, y, x  
          or pls, z  
 
     draws surface plot of Z versus (X,Y) as a filled mesh with  
     optional contours.  The Z array must be a 2-dimensional array,  
     see documentation of pls_mesh for the meaning of X and Y.  
     If keyword CBAR is set to non-zero, a color bar is drawn on the  
     right of the plot.  The current viewport (in NDC) may be  
     specified with keyword VIEWPORT, default is:  
       [0.19, 0.60, 0.44, 0.85].  
     The appearance of the filled mesh can be modified by means of  
     keywords: LEGEND, HIDE, TOP, CMIN, CMAX, EDGES, ECOLOR and EWIDTH  
     (see plf documentation).  
     Optional contour plot of Z may be superimposed by either keyword  
     NLEVS to set the number of contours or by with keyword LEVS to  
     specify the level values.  The appearance of the contour plot can  
     be modified by means of keywords: LEGEND, HIDE, TYPE, WIDTH,  
     COLOR, MARKS, MARKER, MSPACE, MPHASE and SMOOTH (see plc  
     documentation).  

             err_msg= pls_mesh(x, xx, dimsof(z), which=1/2, inhibit=1/2)  
 
     build X and/or XX arrays of coordinates (abscissa if last argument is  
     0/nil; otherwise ordinate) for 2-D array Z.  Normally, the returned  
     value is string(0) otherwise it is an error message.  
     X is input and output, it will have the same shape as Z and will be  
     suitable for contour plots.  XX is purely output, it will have 1 more  
     element than Z in each dimension and will be suitable for mesh plots.  
     In other words, X(i,j) will furnish the coordinate of the centre of  
     cell Z(i,j) whereas XX(i,j), XX(i,j+1), XX(i+1,j) and XX(i+1,j+1)  
     will give the coordinates of the corners of cell Z(i,j).  
     Assuming the length of Z along the considered dimension is N  
     (N must be >= 2) there are 3 possibilities:  
       (1) if X is a vector with N elements or has the same shape as Z,  
           then X is considered to give the coordinates at the centre of Z  
           cells: X is unchanged and output XX is build by interpolating  
	   (and extrapolating at the edges) X ;  
       (2) if X is a vector with N+1 elements or has 1 more element than Z  
           in each dimension, then X is considered to give the coordinates  
           at the corners of Z cells: output XX is set to input X and  
	   output X is build by interpolating output XX;  
       (3) if X is nil, it defaults to [0.5, 1.5, ..., N-0.5] and XX  
           defaults to [0, 1, ..., N] along the considered dimension.  
     Finally, if X is 1-D, it is expanded in the other direction.  
     If keyword WHICH is 1 (the default), abscissa is the dimension of  
     interest; otherwise WHICH must be 2 and ordinate is the dimension  
     of interest.  
     If keyword INHIBIT is 1, then only X output is computed; if INHIBIT  
     is 2 then only XX output is computed.  

             win_copy_lim, src, dst;  
 
     Make limits of window DST the same as those in window SRC.