c
c $Id: llst.f,v 1.2 1999/08/03 21:21:32 aai Exp $.
c
c{
      program llst
c
c     Llst - Test lls() et. al.
c
c     To use this program, compile and link with libfortex77.a then
c     execute and either type in (X,Y) pairs directly or redirect them
c     as standard input, one (X,Y) pair per line.
c
c     Phillip A. Cheeseman, Purdue University Computing Center.
c
c     MAXCAP is the maximum number of points we can keep in the data arrays.
c
      integer MAXCAP
      parameter (MAXCAP=1000)
c
c     Data arrays for (X,Y) pairs.
c
      real x(MAXCAP)
      real y(MAXCAP)
c
c     Least square line parameters.
c
      real a
      real b
      real sigma
c
c     Response code returned by lls() and counter for data points.
c
      integer iresp
      integer n
c
c     Messages we'll return if we get a negative response from lls().
c     Data statements could be done several different ways.  I've
c     chosen the one that'll work anywhere.
c
      character*40 problems(3)
c
      data problems(1) / 'No data points.' /
      data problems(2) / 'Calculation of std. dev. not possible.' /
      data problems(3) / 'Least squares line is vertical.' /
c
c     Preset count of data points then read (X,Y) pairs until end of file
c     or limit of arrays.
c
      n = 0
00011 read(*,*,end=21) x(n+1),y(n+1)
      n = n+1
      if(n.lt.MAXCAP) go to 11
      write(*,'(a,i5)') ' Llst: exceeded array capacity of ',MAXCAP,'.'
c
00021 call lls(n, x, y, iresp, sigma, a, b)
c
c     Here, we issue an error message if iresp is negative.
c     This could be more elegantly done by dropping the trailing blanks
c     but that's more code for messages we shouldn't see too often.
c
      if(iresp.lt.0) then
         write(*,'(a,i2,a)') '  Llst: problem code is (',iresp,').'
         if((iresp.le.-1).and.(iresp.ge.-3)) then
            write(*,'(8x,a)') problems(-iresp)
         endif
      endif
c
c     Write the results.
c
      if((iresp.ge.0).or.(iresp.eq.-2)) then
         write(*,*) ' Llst: A=',a
         write(*,*) '       B=',b
         if(iresp.ne.-2) then
            write(*,*) '       S=',sigma
         endif
      endif
c
      stop
c
      end
c}