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SUBROUTINE GCONTR

 GCONTR draws contour lines of a 2-d array using a technique which produces long, connected contour lines. It assumes that the points of the input array are equally spaced in each dimension. Several options for contouring are provided. When cs, the label character size is positive, the origin point (1,1) is in the lower-left corner and the point (i,j) in the array is plotted at,

      xplot = (i-1)*xl
      yplot = (j-1)*yl
If cs is negative, the x and y values plotted (xp,yp) for the point (i,j) in the array are computed using the  PLT3D  transformation common block  PLT3B (see PLT3D),
        xp = a1 * (yl * j) + a2 * (xl * i) + a3
        yp = b1 * (yl * j) + b2 * (xl * i) + b4
where the vertical height (z) is zero. In this case, xl and yl should be set to 1.0 and PLT3D should be called before GCONTR. GCONTR is used in the MASTER routine  LCNTR and CVAX3DX.  
CALL GCONTR(z,ndx,ndy,nx,ny,xl,yl,cv,nv,zm,iw,n,cs,m,i,ic,il)

z       (R): 2-d array of values dimensioned z(nx,ny)
ndx,ndy (I): dimensions of data array
nx,ny   (I): number of points to use in array
xl,yl   (R): axis length scale factors (inches/array index)
cv      (R): array of contour levels dimensioned cl(nv)
nv      (I): number of contour levels  (note: if nv < 0 then only
             one contour level is used.  It will be labeled with
             the abs(nv)'th symbol)
zm      (R): maximum value of z for consideration.  A z value which
             exceeds this value will be ignored. The cell edges
             which include this point will not be included in
             contouring.
iw      (I): workspace dimensioned at least (2*nx*ny*nv+1)/31
n       (I): contour labeling option
             < 0 label with contour value (number with n digits
                 to the right of the decimal point)
             = 0 no labelling of contours
             > 0 label with alphabet (nl should be less than 26)
cs      (R): size of labels
             < 0 : plot contours using PLT3B transformation
                   xl and yl should then be set to 1.0 (see notes)
             > 0 : normal location specification
m       (I): minimum number of cells crossed by contour in order
             for contour to be labeled
i       (I): color and line type flag
             = 0 color and line type arrays not used
             = 1 color array used
             = 2 line type array used
             = 3 color and line type array used
ic      (I): color list for each contour (only requied for i>0)
l       (I): line type list for contours (accessed only for i>1)



David Long
Wed Jun 12 10:34:11 MDT 1996