SUBROUTINE  PLTMA (X,Y,X0,Y0)

C     [MARGIN ADJUSTER]
C     PLTMA ADJUSTS THE COORDINATES (X0,Y0) TO PROVIDE A HYPERBOLIC
C     TANGENTIAL DISTORTION (X,Y) OF THE OUTER ONE INCH MARGIN OF A
C     GRAPH, SO THE PEN WILL NEVER RUN OVER THE EDGE OF THE PAGE.
C     [02-NOV-73]

      DATA       HX,HY/4.50,3.25/

      X=X0
      IF (X.GT. HX) X= HX+TANH(X-HX)
      IF (X.LT.-HX) X=-HX+TANH(X+HX)
      Y=Y0
      IF (Y.GT. HY) Y= HY+TANH(Y-HY)
      IF (Y.LT.-HY) Y=-HY+TANH(Y+HY)
      RETURN

      END