---

C Library Functions  - smoot (3)

---

NAME

smoot(3f) - [M_calcomp:scientific] draw a polyline using modified spline-fitting technique (LICENSE:PD)

CONTENTS

Synopsis
Description
Options
Description
     Comments
Examples
License

SYNOPSIS

subroutine smoot(xpage,ypage,ipen)

DESCRIPTION

SMOOT is a FORTRAN subroutine which draws a smooth curve through a set of data points. It accomplishes this by using a modified spline-fitting technique. The subroutine receives a single coordinate pair on each call and accumulates the points until it has received a sufficient number to compute a pair of cubic parametric equations for a smooth curve. This accumulation method requires the user to specify an initial and a terminal call to the subroutine.

The SMOOT subroutine operates in either of two modes: Smooth Mode and Plot Mode.

OPTIONS

XPAGE,YPAGE
	are the coordinates, in inches, of a single point through which the pen moves.
IPEN	determines the mode and action of the SMOOT subroutine.

DESCRIPTION

The first call to SMOOT must use an IPEN value of 0 or -1 to put SMOOT in the Smooth Mode.

    if IPEN = 0, XPAGE,YPAGE define the initial point (P(1))
    on the curve. The smoothing function ends at the last
    point (P(n)). An open curve is produced.

    if IPEN = -1, XPAGE,YPAGE are used to define the initial
    point (P(1)) on the curve. The smoothing function
    continues from the last point (P(n)) back to the initial
    point (P(1)). A closed curve is produced.

SMOOTH MODE:

  When SMOOT is in the Smooth Mode, IPEN performs the following functions:

   IPEN = -2       XPAGE,YPAGE are used to define points P(2), P(3),...,
                   P(N-1), and a smoothed curve is drawn through the points
                   on the curve.

   IPEN = -3       XPAGE,YPAGE are used to define points P(2), P(3),
                   ...,P(N-1), and the pen, in the up position, is moved
                   through these points. The smoothing function is
                   maintained.

   IPEN = 2 or 3   The call is treated as a normal CALL PLOT
                   (XPAGE,YPAGE,IPEN), and the point is not considered a
                   point on the curve. The point of departure from the
                   curve is the next-to-last point received by SMOOT, not
                   the last point.

                   When the next call to SMOOT with IPEN = -2 or -3 is
                   received, the pen is repositioned to the point where
                   it left the smooth curve.  The smooth curve is then
                   continued as though the calls with IPEN = 2 or 3 had
                   not occurred.

   IPEN <=(-24)   is used for the terminal call while SMOOT is in the
                  Smooth Mode. XPAGE,YPAGE represent P(N). The curve is
                  finished, and the subroutine returns to the Plot Mode.

PLOT MODE:

SMOOT is in the Plot Mode after receiving a terminal call.

     IF IPEN = +-2 or +-3, the call is treated as a normal CALL
     PLOT (XPAGE,YPAGE,IPEN).

    COMMENTS

When SMOOT is called while it is in the Smooth Mode, the pen is not moved until three points on an open curve or four points on a closed curve have been received. For subsequent calls to SMOOT, the actual pen position is the next-to-last point received.

Calls to other plotting subroutines may be intermixed with calls to SMOOT. Point-of-departure restrictions are the same as noted in the Smooth Mode description above.

The first call to SMOOT must be with IPEN = 0 or -1 .

EXAMPLES

Sample program

   program demo_smoot
   use M_calcomp
   implicit none
   ! based on concepts of CALIFORNIA COMPUTER PRODUCTS, 1968
   real :: xar(10)=[0.75,1.75,2.25,2.75,3.25,4.25,4.75,5.75,0.0,1.0]
   real :: yar(10)=[3.25,2.00,5.25,6.50,6.75,6.25,3.25,4.25,0.0,1.0]
   character(len=50) :: ibcd
   integer           :: inteq
      call plots(0.0,10.0,0.0,10.0)
   !     DRAW FRAME
      call plot(7.0,0.0,2)
      call plot(7.0,9.0,2)
      call plot(0.0,9.0,2)
      call plot(0.0,0.0,2)
   !     DRAW AXIS
      ibcd=’SERVICE TIME’
      call axis(0.75,0.75,ibcd,-12,5.0,0.0,5.0,1.0)
      ibcd=’FREQUENCY’
      call axis(0.75,0.75,ibcd, 9,7.0,90.0,0.0,100.0)
   !     DRAW COMMENTS
      ibcd=’USING FLINE AND SMOOT SUBROUTINES’
      call symbol(0.7,8.25,0.14,ibcd,inteq,0.0,34)
      call plot(5.0,7.8,3)
      call plot(5.1,7.8,2)
      ibcd=’SMOOT’
      call symbol(5.2,7.80,0.09,ibcd,inteq,0.0, 6)
      inteq = 1
      call symbol(5.0,7.60,0.10,ibcd,inteq,0.0,-1)
      inteq=999
      ibcd=’FLINE’
      call symbol(5.2,7.60,0.09,ibcd,inteq,0.0, 5)
   ! SMOOTHING
      call smoot(0.75,3.75,0)
      call smoot(1.75,2.5,-2)
      call smoot(2.25,5.75,-2)
      call smoot(2.75,7.0,-2)
      call smoot(3.25,7.25,-2)
      call smoot(4.25,6.75,-2)
      call smoot(4.75,3.75,-2)
      call smoot(5.75,4.75,-24)
   ! FLINE IS USED
      call plot(0.75,3.25,3)
      call fline(xar, yar, -8,1,1,1)
      call nframe()
   end program demo_smoot

LICENSE

Public Domain

---

Nemo Release 3.1

smoot (3)

February 23, 2025

Generated by manServer 1.08 from ddd61587-660d-4e4b-838b-451182749442 using man macros.