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

# include "nearest_interp_1d.h"
# include "r8lib.h"

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

double *nearest_interp_1d ( int nd, double xd[], double yd[], int ni, 
  double xi[] )

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

    NEAREST_INTERP_1D evaluates the nearest neighbor interpolant.

  Discussion:

    The nearest neighbor interpolant L(ND,XD,YD)(X) is the piecewise
    constant function which interpolates the data (XD(I),YD(I)) for I = 1
    to ND.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    05 September 2012

  Author:

    John Burkardt

  Parameters:

    Input, int ND, the number of data points.
    ND must be at least 1.

    Input, double XD[ND], the data points.

    Input, double YD[ND], the data values.

    Input, int NI, the number of interpolation points.

    Input, double XI[NI], the interpolation points.

    Output, double NEAREST_INTERP_1D[NI], the interpolated values.
*/
{
  double d;
  double d2;
  int i;
  int j;
  int k;
  double *yi;

  yi = ( double * ) malloc ( ni * sizeof ( double ) );

  for ( i = 0; i < ni; i++ )
  {
    k = 0;
    d = fabs ( xi[i] - xd[k] );
    for ( j = 1; j < nd; j++ )
    {
      d2 = fabs ( xi[i] - xd[j] );
      if ( d2 < d )
      {
        k = j;
        d = d2;
      }
    }
    yi[i] = yd[k];
  }

  return yi;
}