lasp/cpp_src/dsp/lasp_window.cpp

// lasp_window.cpp
//
// Author: J.A. de Jong - ASCEE
//
/* #define DEBUGTRACE_ENABLED */
#include "debugtrace.hpp"
#include "lasp_window.h"

using rte = std::runtime_error;
using std::cerr;
using std::endl;

// Safe some typing. Linspace form 0 up to (and NOT including N).
#define lin0N arma::linspace(0, N - 1, N)

vd Window::hann(const us N) {
  return arma::pow(arma::sin((arma::datum::pi/N) * lin0N), 2);
}
vd Window::hamming(const us N) {
  d alpha = 25.0 / 46.0;
  return alpha - (1 - alpha) * arma::cos(2 * number_pi * lin0N / N);
}
vd Window::blackman(const us N) {
  d a0 = 7938. / 18608.;
  d a1 = 9240. / 18608.;
  d a2 = 1430. / 18608.;
  return a0 - a1 * d_cos((2 * number_pi/N) * lin0N) +
         a2 * d_cos((4 * number_pi / N)* lin0N );
}

vd Window::rectangular(const us N) { return arma::ones(N); }

vd Window::bartlett(const us N) {
  return 1 - arma::abs(2 * (lin0N - (N - 1) / 2.) / N);
}
vd Window::create(const WindowType w, const us N) {

  switch (w) {
  case WindowType::Hann: {
    return hann(N);
    break;
  }
  case WindowType::Hamming: {
    return hamming(N);
    break;
  }
  case WindowType::Rectangular: {
    return rectangular(N);
    break;
  }
  case WindowType::Bartlett: {
    return bartlett(N);
    break;
  }
  case WindowType::Blackman: {
    return blackman(N);
    break;
  }
  default:
    abort();
    break;
  }
}