SUBROUTINE  PLTRI (X,Y,L)

C     [RECTANGULAR INCREMENTAL GRAPH]
C     PLOT A RECTANGULAR GRAPH POINT BY POINT. PEN ORIGIN IS ASSUMED
C     TO BE THE CENTER OF A PAGE WHOSE DIMENSIONS ARE 2*HX X 2*HY.THE
C     OPTIONS AFFORDED BY L ARE:
C       L=1   (X1,Y1) RESPECTIVE LOWER LIMITS
C       L=2   (X2,Y2) RESPECTIVE UPPER LIMITS
C       L=3   FIRST POINT OF A SERIES
C       L=4   SUBSEQUENT POINTS
C       L=5   RECTANGULAR AXES THROUGH (X,Y)
C       L=6   TICK MARK AT (X,Y)
C       L=7   LARGER TICK MARK
C     AS LONG AS OPTIONS 6 AND 7 CALL PLTMC AND THE OTHERS CALL PLTMS,
C     TICK MARKS MAY BE PLACED IN ANY ORDER-BUT NOT BEFORE THE LIMITS
C     HAVE BEEN ESTABLISHED. THE LIMITS MUST BE DEFINED BEFORE STARTING
C     THE GRAPH.  THE INITIAL POINT SHOULD ONLY BE ENTERED BY OPTION
C     3, WHICH MAY ALSO BE USED TO CREATE GAPS IN THE GRAPH, OR TO
C     INIATE A NEW CURVE.  TO SUPPRESS ONE OF THE AXES DRAWN BY OPTION
C     5, CHOOSE A CROSSING POINT OUTSIDE OF THE RANGE OF THE GRAPH.
C     [10-NOV-74]

      EXTERNAL     PLTMC
      DATA         HX,HY/4.50,3.25/

      EX(X)=(X-X1)*SX-HX
      WY(Y)=(Y-Y1)*SY-HY

      GO TO (10,20,5,40,5,5,5),L
    5 SX=(2.0*HX)/(X2-X1)
      SY=(2.0*HY)/(Y2-Y1)
      GO TO (7,7,30,7,50,60,70),L
    7 RETURN

   10 X1=X
      Y1=Y
      RETURN
   20 X2=X
      Y2=Y
      RETURN
   30 CALL PLTMS (EX(X),WY(Y),.FALSE.)
      RETURN
   40 CALL PLTMS (EX(X),WY(Y),.TRUE.)
      RETURN
   50 CALL PLTMS (-HX,WY(Y),.FALSE.)
      CALL PLTMS ( HX,WY(Y),.TRUE.)
      CALL PLTMS (EX(X), HY,.FALSE.)
      CALL PLTMS (EX(X),-HY,.TRUE.)
      RETURN
   60 CALL PLTFM (EX(X),WY(Y),0.04,PLTMC)
      RETURN
   70 CALL PLTFM (EX(X),WY(Y),0.06,PLTMC)
      RETURN

      END