program main

c*****************************************************************************80
c
cc correlation_heat_map() creates a heat map of correlation matrix data.
c
c  Licensing:
c
c    This code is distributed under the MIT license.
c
c  Modified:
c
c    24 April 2025
c
c  Author:
c
c    John Burkardt
c
      implicit none

      double precision cmax
      double precision cmin
      character ( len = 80 ) command_filename
      integer command_unit
      double precision xmax
      double precision xmin
      double precision ymax
      double precision ymin

      call timestamp ( )
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 'correlation_heat_map():'
      write ( *, '(a)' ) '  Fortran77 version'
      write ( *, '(a)' ) 
     &  '  Heat map of a correlation matrix using gnuplot().'

      cmin = 0.28
      cmax = 1.00

      call get_unit ( command_unit )
      command_filename = 'correlation_heat_map_commands.txt'
      open ( unit = command_unit, file = command_filename, 
     &  status = 'replace' )
      write ( command_unit, '(a)' ) '# ' // trim ( command_filename )
      write ( command_unit, '(a)' ) '#'
      write ( command_unit, '(a)' ) '# Usage:'
      write ( command_unit, '(a)' ) '#  gnuplot < ' // 
     &  trim ( command_filename )
      write ( command_unit, '(a)' ) '#'
      write ( command_unit, '(a)' ) 'set term png'
      write ( command_unit, '(a)' ) 
     &  'set output "correlation_heat_map.png"'
      write ( command_unit, '(a)' ) 
     &  'set title "Heat map of correlation matrix"'
      write ( command_unit, '(a)' ) 'unset key'
      write ( command_unit, '(a)' ) 'set tic scale 0'
      write ( command_unit, '(a)' ) 'set palette rgbformula 21, 22, 23'
      write ( command_unit, '(a,f8.2,a,f8.2,a)' ) 
     &  'set cbrange [', cmin, ':', cmax, ']'
      write ( command_unit, '(a)' ) 'unset cbtics'
c
c  These relate to the 1x8 range of i and j.
c
      xmin = -0.5
      xmax = 7.5
      ymin = -0.5
      ymax = 7.5
      write ( command_unit, '(a,f8.2,a,f8.2,a)' ) 
     &  'set xrange [', xmin, ':', xmax, ']'
      write ( command_unit, '(a,f8.2,a,f8.2,a)' ) 
     &  'set yrange [', ymax, ':', ymin, ']'
      write ( command_unit, '(a)' ) 'set size square'
      write ( command_unit, '(a)' ) 'set view map'
      write ( command_unit, '(a)' ) 
     &  'splot "correlation_data.txt" matrix with image'
      write ( command_unit, '(a)' ) 'quit'
      close ( unit = command_unit )
      write ( *, '(a)' ) '  Created command file "' // 
     &  trim ( command_filename ) // '".'
c
c  Terminate.
c
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 'correlation_heat_map():'
      write ( *, '(a)' ) '  Normal end of execution.'
      write ( *, '(a)' ) ''
      call timestamp ( )

      stop
      end
      subroutine get_unit ( iunit )

c*********************************************************************72
c
cc get_unit() returns a free Fortran unit number.
c
c  Discussion:
c
c    A "free" Fortran unit number is a value between 1 and 99 which
c    is not currently associated with an I/O device.  A free Fortran unit
c    number is needed in order to open a file with the OPEN command.
c
c    If IUNIT = 0, then no free Fortran unit could be found, although
c    all 99 units were checked (except for units 5, 6 and 9, which
c    are commonly reserved for console I/O).
c
c    Otherwise, IUNIT is a value between 1 and 99, representing a
c    free Fortran unit.  The code assumes that units 5 and 6
c    are special, and will never return those values.
c
c  Licensing:
c
c    This code is distributed under the MIT license.
c
c  Modified:
c
c    02 September 2013
c
c  Author:
c
c    John Burkardt
c
c  Output:
c
c    integer IUNIT, the free unit number.
c
      implicit none

      integer i
      integer iunit
      logical value

      iunit = 0

      do i = 1, 99

        if ( i .ne. 5 .and. i .ne. 6 .and. i .ne. 9 ) then

          inquire ( unit = i, opened = value, err = 10 )

          if ( .not. value ) then
            iunit = i
            return
          end if

        end if

10      continue

      end do

      return
      end
      subroutine r8vec_linspace ( n, a, b, x )

c*****************************************************************************80
c
cc r8vec_linspace() creates a vector of linearly spaced values.
c
c  Discussion:
c
c    An R8VEC is a vector of R8's.
c
c    4 points evenly spaced between 0 and 12 will yield 0, 4, 8, 12.
c
c    In other words, the interval is divided into N-1 even subintervals,
c    and the endpoints of intervals are used as the points.
c
c  Licensing:
c
c    This code is distributed under the MIT license.
c
c  Modified:
c
c    14 March 2011
c
c  Author:
c
c    John Burkardt
c
c  Input:
c
c    integer N, the number of entries in the vector.
c
c    double precision A_FIRST, A_LAST, the first and last entries.
c
c  Output:
c
c    double precision X(N), a vector of linearly spaced data.
c
      implicit none

      integer n

      double precision a
      double precision b
      integer i
      double precision x(n)

      if ( n == 1 ) then

        x(1) = ( a + b ) / 2.0D+00

      else

        do i = 1, n
          x(i) = ( dble ( n - i     ) * a
     &           + dble (     i - 1 ) * b )
     &           / dble ( n     - 1 )
        end do

      end if

      return
      end
      subroutine timestamp ( )

c*********************************************************************72
c
cc timestamp() prints the YMDHMS date as a timestamp.
c
c  Licensing:
c
c    This code is distributed under the MIT license.
c
c  Modified:
c
c    12 June 2014
c
c  Author:
c
c    John Burkardt
c
      implicit none

      character * ( 8 ) ampm
      integer d
      character * ( 8 ) date
      integer h
      integer m
      integer mm
      character * ( 9 ) month(12)
      integer n
      integer s
      character * ( 10 ) time
      integer y

      save month

      data month /
     &  'January  ', 'February ', 'March    ', 'April    ', 
     &  'May      ', 'June     ', 'July     ', 'August   ', 
     &  'September', 'October  ', 'November ', 'December ' /

      call date_and_time ( date, time )

      read ( date, '(i4,i2,i2)' ) y, m, d
      read ( time, '(i2,i2,i2,1x,i3)' ) h, n, s, mm

      if ( h .lt. 12 ) then
        ampm = 'AM'
      else if ( h .eq. 12 ) then
        if ( n .eq. 0 .and. s .eq. 0 ) then
          ampm = 'Noon'
        else
          ampm = 'PM'
        end if
      else
        h = h - 12
        if ( h .lt. 12 ) then
          ampm = 'PM'
        else if ( h .eq. 12 ) then
          if ( n .eq. 0 .and. s .eq. 0 ) then
            ampm = 'Midnight'
          else
            ampm = 'AM'
          end if
        end if
      end if

      write ( *, 
     &  '(i2,1x,a,1x,i4,2x,i2,a1,i2.2,a1,i2.2,a1,i3.3,1x,a)' ) 
     &  d, trim ( month(m) ), y, h, ':', n, ':', s, '.', mm, 
     &  trim ( ampm )

      return
      end