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C Library Functions  - fit (3)

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NAME

fit(3f) - [M_calcomp:general] draws a semi-hyperbolic curve through three points (LICENSE:PD)

CONTENTS

Synopsis
Description
Options
Comments
Restrictions
Examples
License

SYNOPSIS

subroutine fit(xpage1,ypage1,xpage2,ypage2,xpage3,ypage3)

DESCRIPTION

FIT is a FORTRAN subroutine which draws a semi-hyperbolic curve through three points.

OPTIONS

XPAGE1,YPAGE1
	are the X and Y coordinates, in inches, of the three
XPAGE2,YPAGE2
	points through which the curve passes. XPAGE3,YPAGE3

COMMENTS

This subroutine generates a semi-hyperbolic fit using the three given points. A set of points for which a fit is not possible is drawn with straight-line segments.

RESTRICTIONS

The curve through the three points must be multi-valued in both X and Y. That is, the middle point (XPAGE2,YPAGE2) must be between the endpoints along the X-axis or the Y-axis.

       XPAGE1<YPAGE2<XPAGE3 or XPAGE1>XPAGE2>XPAGE3 or
       YPAGE1<YPAGE2<YPAGE3 or YPAGE1>YPAGE2>YPAGE3

EXAMPLES

Sample program:

   program demo_fit
   use M_calcomp, only : plots, plot, newpen, width, fit
   !use M_calcomp, only : black ,red ,green ,yellow, purple ,magenta ,cyan ,white
   use M_calcomp, only : green, red, yellow, magenta, green
   implicit none
   integer,parameter  :: MOVE=3, DRAW=2
   integer            :: i
   real               :: x(3)=[-3.0,1.0,4.4],y(3)=[3.2,1.0,-4.0]
   call plots(0.0,10.0,0.0,10.0)      ! initialize graphics
   call plot(5.0,5.0,-3)              ! set origin
   call newpen(green)
   call crosshair(0.0,0.0,2.0)        ! draw a crosshair at origin point <0,0>
   call width(30); call newpen(red)
   do i=1,size(x)                     ! mark the points
      call crosshair(x(i),y(i),0.2)
   enddo
   x=[-3.0, 1.0, 4.4]
   y=[ 3.2, 1.0,-4.0]
   call width(80); call newpen(yellow)
   call fit(x(2),y(2),x(3),y(3),x(1),y(1))   ! draw in wrong order
   call width(40);call newpen(magenta)
   call fit(x(2),y(2),x(1),y(1),x(3),y(3))   ! draw in wrong order
   call width(140); call newpen(green)
   call fit(x(1),y(1),x(2),y(2),x(3),y(3))   ! draw in right order to get fit
   call plot(0.0,0.0,999)                    ! terminate graphics and pause
   contains
   subroutine crosshair(x,y,s)
   real,intent(in) :: x,y,s
       call plot(x+s,y    ,MOVE)
       call plot(x-s,y    ,DRAW)
       call plot(x    ,y+s,MOVE)
       call plot(x    ,y-s,DRAW)
   end subroutine crosshair
   end program demo_fit

LICENSE

Public Domain

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Nemo Release 3.1

fit (3)

February 23, 2025

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