C
      SUBROUTINE draw_axes(xmin,xmax,ymin,ymax)
      IMPLICIT NONE
      REAL x0,y0,xmin,xmax,ymin,ymax,dx,dy,tx,ty,x,y
      INTEGER IR_, itick, ntick
      ntick = 10                            ! number of tick marks
*      distance between tick marks on x-axis
      dx = (xmax - xmin)/ntick
*      distance between tick marks on y-axis
      dy = (ymax - ymin)/ntick
*      include margin
      CALL GWindow(IR_, xmin - dx, ymin - dy, xmax + dx, ymax + dy)
      x0 = max(0.0,xmin)
      IF(ymin*ymax .LT. 0) then
         y0 = 0
      ELSE
         y0 = ymin
      END IF
      CALL GWline(IR_, xmin, y0, xmax, y0)  ! horizontal axis
      CALL GWline(IR_, x0, ymin, x0, ymax)  ! vertical axis
      tx = 0.1*dy                           ! size of tick mark
      ty = 0.1*dx
      DO itick = 0, ntick
          x = xmin + itick*dx
          CALL GWline(IR_, x, y0 - tx, x, y0 + tx)
*                                             draw ticks on x axis
          y = ymin + itick*dy
          CALL GWline(IR_, x0 - ty, y, x0 + ty, y)
*                                             draw ticks on y axis
      ENDDO
      END
C
      SUBROUTINE compute_aspect_ratio(r,x,y)
      IMPLICIT NONE
      REAL aspect_ratio, m, size, r, x, y
      INTEGER IR_, px, py
      m = 0.1*r                             ! margin
      size = r + m
*     px, py: # pixels in horizonal and vertical direction
      CALL GWsize(IR_, 7, px,py)
      IF(px .GT. py) THEN
         aspect_ratio = REAL(px)/py
         x = aspect_ratio*size
         y = size
      ELSE
         aspect_ratio = REAL(py)/px
         x = size
         y = aspect_ratio*size
      END IF
      END