| 
	    pltr1
	  ( | x, | 
| y, | |
| tx, | |
| ty, | |
| pltr_data ); | 
Linear interpolation for matrix index to world coordinate mapping using
    one-dimensional x and y
    coordinate arrays.  This routine can be used for the
    PLTRANSFORM_callback argument of plcont, plshade, plshades,
    plimagefr, or plvect.
x
	  (PLFLTX index of matrix.
y
	  (PLFLTY index of matrix.
tx
	  (PLFLT_NC_SCALARTransformed x value in world coordinates corresponding to x index of matrix.
ty
	  (PLFLT_NC_SCALARTransformed y value in world coordinates corresponding to y index of matrix.
pltr_data
	  (PLPointerA pointer to additional data that is passed as an
	  argument to PLplot routines that potentially could use the pltr1
	  callback (i.e., plcont, plimagefr, plshade,
	  plshades, and plvect); which then internally pass that argument on
	  to this callback.
This function is used in C examples 9 and 16.