SUBROUTINE  PLTFI (Y1,WY,Y2,N)

C     [FUNCTION OF INTEGERS]
C     PLOT A GRAPH IN RECTANGULAR COORDINATES, BY CONNECTING SUCCESSIVE
C     DATA POINTS BY STRAIGHT LINES. THE POINTS DEFINING THE GRAPH ARE
C     TAKEN FROM AN ARRAY OF Y-VALUES. THE X-VALUES ARE INTEGERS, LYING
C     BETWEEN 1 AND N. THE RESPECTIVE SCALES ARE INDICATED BY THE VALUES
C     TO BE ASSIGNED TO THE MARGINS OF THE GRAPH. ORDINARILY THE MARGINS
C     WOULD BE GIVEN ROUNDED VALUES SLIGHTLY LARGER THAN THE EXTREME
C     DATA VALUES.  HOWEVER, THE GRAPH MAY BE CENTERED IN VARIOUS WAYS
C     BY ASSIGNING THE Y-MARGINS CONSIDERABLY LARGER VALUES. LIKEWISE
C     EXCERPTS FROM THE GRAPH MAY BE CHOSEN BY GIVING THE Y-MARGINS
C     LESSER VALUES THAN THE EXTREMES.  THE X-RANGE CANNOT BE ALTERED,
C     THE MARGINS BEING FIXED AT 1 AND N.  HOWEVER, THE SUBROUTINE CAN
C     BE CALLED USING A SUBARRAY OF WY AS ITS ARGUMENT, OR WY COULD BE
C     EMBEDDED IN A LARGER ARRAY USING AN EQUIVALENCE. ON THE OTHER HAND
C     PLTRG OR PLTRI SHOULD PROBABLY BE USED WHEN IT IS NOT SATISFACTORY
C     TO GRAPH THE ARRAY AS IT STANDS.
C     Y1     Y LOWER LIMIT
C     WY(N)  ARRAY OF Y VALUES
C     Y2     Y UPPER LIMIT
C     N      NUMBER OF POINTS
C     [16-JAN-75]

      DIMENSION   WY(1)

      IF (N.LT.2) RETURN
      CALL PLTRI (1.0,Y1,1)
      CALL PLTRI (FLOAT(N),Y2,2)
      CALL PLTRI (1.0,WY(1),3)
      DO 10 I=2,N
   10 CALL PLTRI (FLOAT(I),WY(I),4)
      RETURN

      END