# PGPLOT Module: PGVECT -- vector map of a 2D data array, with blanking

SUBROUTINE PGVECT (A, B, IDIM, JDIM, I1, I2, J1, J2, C, NC, TR,
1 BLANK)
INTEGER IDIM, JDIM, I1, I2, J1, J2, NC
REAL A(IDIM,JDIM), B(IDIM, JDIM), TR(6), BLANK, C

Draw a vector map of two arrays. This routine is similar to
PGCONB in that array elements that have the "magic value" defined by
the argument BLANK are ignored, making gaps in the vector map. The
routine may be useful for data measured on most but not all of the
points of a grid. Vectors are displayed as arrows; the style of the
arrowhead can be set with routine PGSAH, and the the size of the
arrowhead is determined by the current character size, set by PGSCH.

Arguments
A (input) : horizontal component data array.
B (input) : vertical component data array.
IDIM (input) : first dimension of A and B.
JDIM (input) : second dimension of A and B.
I1,I2 (input) : range of first index to be mapped (inclusive).
J1,J2 (input) : range of second index to be mapped (inclusive).
C (input) : scale factor for vector lengths, if 0.0, C will be
set so that the longest vector is equal to the
smaller of TR(2)+TR(3) and TR(5)+TR(6).
NC (input) : vector positioning code.
<0 vector head positioned on coordinates
>0 vector base positioned on coordinates
=0 vector centered on the coordinates
TR (input) : array defining a transformation between the I,J
grid of the array and the world coordinates. The
world coordinates of the array point A(I,J) are
given by:
X = TR(1) + TR(2)*I + TR(3)*J
Y = TR(4) + TR(5)*I + TR(6)*J
Usually TR(3) and TR(5) are zero - unless the
coordinate transformation involves a rotation
or shear.
BLANK (input) : elements of arrays A or B that are exactly equal to
this value are ignored (blanked).