lasp/cpp_src/dsp/lasp_freqsmooth.cpp
J.A. de Jong - Redu-Sone B.V., ASCEE V.O.F ab080910fc
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Made power correction in smoothing algorithm optional. Window decreases in size symmetrically around the edged of the frequency spectrum
2024-03-12 11:19:52 +01:00

133 lines
3.7 KiB
C++

// #define DEBUGTRACE_ENABLED
#include "lasp_freqsmooth.h"
#include <cassert>
#include "debugtrace.hpp"
using rte = std::runtime_error;
vd freqSmooth(const vd& freq, const vd& X, const unsigned w,
bool power_correct) {
DEBUGTRACE_ENTER;
if (freq.size() < 2) {
throw rte("Invalid frequency size. Should be > 2");
}
if (freq.size() != X.size()) {
throw rte("Sizes of freq and X do not match");
}
if (freq.size() > std::numeric_limits<long>::max() / 2) {
throw rte("Frequency size limit for smoothing is 2^30");
}
if (w == 0) {
throw rte("Invalid number of octaves");
}
const us Nfreq = freq.size();
// Smoothing width in unit of number of octaves
const d Delta = 1 / d(w);
// Minimum frequency and maximum frequency to smooth on (frequency range that
// is interpolated to a log scale)
d freq_min;
const d freq_max = freq(Nfreq - 1);
const bool firstFreqEqZero = (d_abs(freq(0)) < 1e-15);
// AC-signal power
d ac_pwr;
if (firstFreqEqZero) {
freq_min = freq(1);
if (power_correct) {
ac_pwr = arma::sum(X.subvec(1, Nfreq - 1));
}
} else {
freq_min = freq(0);
if (power_correct) {
ac_pwr = arma::sum(X);
}
}
DEBUGTRACE_PRINT(freq_min);
DEBUGTRACE_PRINT(freq_max);
const vd freq_log =
arma::logspace(d_log10(freq_min), d_log10(freq_max), 10 * Nfreq);
DEBUGTRACE_PRINT("freq_log = ");
const long Nfreq_sm = freq_log.size();
// Interpolate X to logscale
vd X_log;
DEBUGTRACE_PRINT("X_log = :");
arma::interp1(freq, X, freq_log, X_log, "*linear");
// First and last point are not interpolated well, could be minimally out of
// the interpolation range, due to roundoff errors. Armadillo sets these
// points to nan, so we have to manually "interpolate" them.
X_log(Nfreq_sm - 1) = X(X.size() - 1);
if (firstFreqEqZero) {
X_log(0) = X(1);
} else {
X_log(0) = X(0);
}
// Allocate space for smoothed X on log scale
vd Xsm_log(freq_log.size());
const d beta = d_log10(Nfreq_sm) / d_log10(2) / (Nfreq_sm - 1);
// int rounds down
const long mu = int(Delta / d(2) / beta);
DEBUGTRACE_PRINT(mu);
// Long is at least 32 bits. So +/- 2M points length
for (long k = 0; k < Nfreq_sm; k++) {
// const d fcur = freq_log(k);
long idx_start = std::max(k - mu, 0l);
long idx_stop = std::min(k + mu, Nfreq_sm - 1);
// Make window smaller at the sides (close to the end of the array)
if (idx_start == 0 || idx_stop == Nfreq_sm - 1) {
const long mu_edge = std::min(k - idx_start, idx_stop - k);
idx_start = k - mu_edge;
idx_stop = k + mu_edge;
}
assert(idx_stop < Nfreq_sm);
assert(idx_start < Nfreq_sm);
DEBUGTRACE_PRINT(idx_start)
DEBUGTRACE_PRINT(idx_stop);
Xsm_log(k) = arma::mean(X_log.subvec(idx_start, idx_stop));
}
DEBUGTRACE_PRINT("Xsm_log:");
// std::cerr << Xsm_log << std::endl;
// Back-interpolate to a linear scale, and be wary of nans at the start end
// and range. Also interpolates power
vd Xsm(Nfreq);
if (firstFreqEqZero) {
vd Xsm_gt0;
arma::interp1(freq_log, Xsm_log, freq.subvec(1, Nfreq - 1), Xsm_gt0,
"*linear");
Xsm(0) = X(0);
Xsm.subvec(1, Nfreq - 1) = Xsm_gt0;
Xsm(1) = Xsm_log(1);
Xsm(Nfreq - 1) = Xsm_log(Nfreq_sm - 1);
// Final step: power-correct smoothed spectrum
if (power_correct) {
d new_acpwr = arma::sum(Xsm.subvec(1, Nfreq - 1));
Xsm.subvec(1, Nfreq - 1) *= ac_pwr / new_acpwr;
}
} else {
arma::interp1(freq_log, Xsm_log, freq, Xsm, "*linear");
Xsm(0) = X(0);
Xsm(Nfreq - 1) = Xsm_log(Nfreq_sm - 1);
// Final step: power-correct smoothed spectrum
if (power_correct) {
d new_acpwr = arma::sum(Xsm);
Xsm *= ac_pwr / new_acpwr;
}
}
return Xsm;
}