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Gaussian smoothening of 1D signal in C++
#pragma once
#include <cmath>
#include <vector>
#include <assert.h>
inline double gauss(double sigma, double x) {
double expVal = -1 * (pow(x, 2) / pow(2 * sigma, 2));
double divider = sqrt(2 * M_PI * pow(sigma, 2));
return (1 / divider) * exp(expVal);
}
inline std::vector<double> gaussKernel(int samples, double sigma) {
std::vector<double> v;
bool doubleCenter = false;
if (samples % 2 == 0) {
doubleCenter = true;
samples--;
}
int steps = (samples - 1) / 2;
double stepSize = (3 * sigma) / steps;
for (int i = steps; i >= 1; i--) {
v.push_back(gauss(sigma, i * stepSize * -1));
}
std::cout << std::endl;
v.push_back(gauss(sigma, 0));
if (doubleCenter) {
v.push_back(gauss(sigma, 0));
}
for (int i = 1; i <= steps; i++) {
v.push_back(gauss(sigma, i * stepSize));
}
std::cout << "The kernel contains " << v.size() << " entries:";
for (auto it = v.begin(); it != v.end(); ++it) {
std::cout << ' ' << *it;
}
std::cout << std::endl;
assert(v.size() == samples);
return v;
}
inline std::vector<double> gaussSmoothen(std::vector<double> values, double sigma, int samples) {
std::vector<double> out;
auto kernel = gaussKernel(samples, sigma);
int sampleSide = samples / 2;
int valueIdx = samples / 2 + 1;
unsigned long ubound = values.size();
for (unsigned long i = 0; i < ubound; i++) {
double sample = 0;
int sampleCtr = 0;
std::cout << "Now at value" << i << ": ";
for (long j = i - sampleSide; j <= i + sampleSide; j++) {
std::cout << j << " ";
if (j > 0 && j < ubound) {
int sampleWeightIndex = sampleSide + (j - i);
std::cout << "(" << sampleWeightIndex << " [" << kernel[sampleWeightIndex] << "]) ";
sample += kernel[sampleWeightIndex] * values[j];
sampleCtr++;
}
}
double smoothed = sample / (double)sampleCtr;
std::cout << " S: " << sample << " C: " << sampleCtr << " V: " << values[i] << " SM: " << smoothed << std::endl;
out.push_back(smoothed);
}
return out;
}
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