# include <math.h>
# include <stdio.h>
# include <stdlib.h>
# include <string.h>
# include <time.h>

int main ( );
double *r8vec_linspace_new ( int n, double a, double b );
void timestamp ( );

/******************************************************************************/

int main ( )

/******************************************************************************/
/*
  Purpose:

    correlation_heat_map() creates a heat map of a correlation matrix.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    24 April 2025

  Author:

    John Burkardt
*/
{
  double cmax;
  double cmin;
  FILE *command_unit;
  double xmax;
  double xmin;
  double ymax;
  double ymin;

  timestamp ( );
  printf ( "\n" );
  printf ( "correlation_heat_map():\n" );
  printf ( "  C version\n" );
  printf ( "  Heat map of a correlation matrix using gnuplot().\n" );

  cmin = 0.28;
  cmax = 1.00;

  command_unit = fopen ( "correlation_heat_map_commands.txt", "wt" );
  fprintf ( command_unit, "# correlation_heat_map_commands.txt\n" );
  fprintf ( command_unit, "#\n" );
  fprintf ( command_unit, "# Usage:\n" );
  fprintf ( command_unit, "#  gnuplot < correlation_heat_map_commands.txt\n" );
  fprintf ( command_unit, "#\n" );
  fprintf ( command_unit, "set term png\n" );
  fprintf ( command_unit, "set output 'correlation_heat_map.png'\n" );
  fprintf ( command_unit, "set xlabel '<--- X --->'\n" );
  fprintf ( command_unit, "set ylabel '<--- Y --->'\n" );
  fprintf ( command_unit, "set title 'Heat map of correlation data'\n" );
  fprintf ( command_unit, "unset key\n" );
  fprintf ( command_unit, "set tic scale 0\n" );
  fprintf ( command_unit, "set palette rgbformula 21, 22, 23\n" );
  fprintf ( command_unit, "set cbrange [%f:%f]\n", cmin, cmax );
  fprintf ( command_unit, "unset cbtics\n" );
/*
  These relate to the 1x8 range of i and j.
*/
  xmin = -0.5;
  xmax = 7.5;
  ymin = -0.5;
  ymax = 7.5;
  fprintf ( command_unit, "set xrange [%f:%f]\n", xmin, xmax );
  fprintf ( command_unit, "set yrange [%f:%f]\n", ymax, ymin );
  fprintf ( command_unit, "set size square\n" );
  fprintf ( command_unit, "set view map\n" );
  fprintf ( command_unit, "splot 'correlation_data.txt' matrix with image\n" );
  fprintf ( command_unit, "quit\n" );
  fclose ( command_unit );
  printf ( "  Created command file 'correlation_heat_map_commands.txt'\n" );
/*
  Terminate.
*/
  printf ( "\n" );
  printf ( "correlation_heat_map():\n" );
  printf ( "  Normal end of execution.\n" );
  timestamp ( );

  return 0;
}
/******************************************************************************/

double *r8vec_linspace_new ( int n, double a, double b )

/******************************************************************************/
/*
  Purpose:

    r8vec_linspace_new() creates a vector of linearly spaced values.

  Discussion:

    An R8VEC is a vector of R8's.

    4 points evenly spaced between 0 and 12 will yield 0, 4, 8, 12.
 
    In other words, the interval is divided into N-1 even subintervals,
    and the endpoints of intervals are used as the points.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    29 March 2011

  Author:

    John Burkardt

  Input:

    int N, the number of entries in the vector.

    double A, B, the first and last entries.

  Output:

    double R8VEC_LINSPACE_NEW[N], a vector of linearly spaced data.
*/
{
  int i;
  double *x;

  x = ( double * ) malloc ( n * sizeof ( double ) );

  if ( n == 1 )
  {
    x[0] = ( a + b ) / 2.0;
  }
  else
  {
    for ( i = 0; i < n; i++ )
    {
      x[i] = ( ( double ) ( n - 1 - i ) * a 
             + ( double ) (         i ) * b ) 
             / ( double ) ( n - 1     );
    }
  }
  return x;
}
/******************************************************************************/

void timestamp ( )

/******************************************************************************/
/*
  Purpose:
 
    timestamp() prints the current YMDHMS date as a time stamp.

  Example:

    17 June 2014 09:45:54 AM

  Licensing:

    This code is distributed under the MIT license. 

  Modified:

    01 May 2021

  Author:

    John Burkardt
*/
{
# define TIME_SIZE 40

  static char time_buffer[TIME_SIZE];
  const struct tm *tm;
  time_t now;

  now = time ( NULL );
  tm = localtime ( &now );

  strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm );

  printf ( "%s\n", time_buffer );

  return;
# undef TIME_SIZE
}