Machine Learning Algorithms

Files
file	adaline_learning.cpp
	Adaptive Linear Neuron (ADALINE) implementation
file	kohonen_som_topology.cpp
	Kohonen self organizing map (topological map)
file	kohonen_som_trace.cpp
	Kohonen self organizing map (data tracing)

Namespaces
namespace	machine_learning
	A* search algorithm

Functions
double	_random (double a, double b)
int	save_2d_data (const char *fname, const std::vector< std::valarray< double > > &X)
void	get_min_2d (const std::vector< std::valarray< double > > &X, double *val, int *x_idx, int *y_idx)
int	save_nd_data (const char *fname, const std::vector< std::valarray< double > > &X)

Variables
constexpr int	MAX_ITER = 500

Detailed Description

Function Documentation

_random()

double _random	(	double	a,
		double	b )

Helper function to generate a random number in a given interval.
Steps:

1. r1 = rand() % 100 gets a random number between 0 and 99
2. r2 = r1 / 100 converts random number to be between 0 and 0.99
3. scale and offset the random number to given range of \([a,b]\)

Parameters

[in]	a	lower limit
[in]	b	upper limit

Returns

random number in the range \([a,b]\)

                                   {
    return ((b - a) * (std::rand() % 100) / 100.f) + a;
}

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get_min_2d()

void get_min_2d	(	const std::vector< std::valarray< double > > &	X,
		double *	val,
		int *	x_idx,
		int *	y_idx )

Get minimum value and index of the value in a matrix

Parameters

[in]	X	matrix to search
[in]	N	number of points in the vector
[out]	val	minimum value found
[out]	idx_x	x-index where minimum value was found
[out]	idx_y	y-index where minimum value was found

                                        {
    val[0] = INFINITY;  // initial min value
    size_t N = X.size();
 
    for (int i = 0; i < N; i++) {  // traverse each x-index
        auto result = std::min_element(std::begin(X[i]), std::end(X[i]));
        double d_min = *result;
        std::ptrdiff_t j = std::distance(std::begin(X[i]), result);
 
        if (d_min < val[0]) {  // if a lower value is found
                               // save the value and its index
            x_idx[0] = i;
            y_idx[0] = j;
            val[0] = d_min;
        }
    }
}

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save_2d_data()

int save_2d_data	(	const char *	fname,
		const std::vector< std::valarray< double > > &	X )

Save a given n-dimensional data martix to file.

Parameters

[in]	fname	filename to save in (gets overwriten without confirmation)
[in]	X	matrix to save

Returns

0 if all ok

-1 if file creation failed

                                                          {
    size_t num_points = X.size();       // number of rows
    size_t num_features = X[0].size();  // number of columns
 
    std::ofstream fp;
    fp.open(fname);
    if (!fp.is_open()) {
        // error with opening file to write
        std::cerr << "Error opening file " << fname << ": "
                  << std::strerror(errno) << "\n";
        return -1;
    }
 
    // for each point in the array
    for (int i = 0; i < num_points; i++) {
        // for each feature in the array
        for (int j = 0; j < num_features; j++) {
            fp << X[i][j];               // print the feature value
            if (j < num_features - 1) {  // if not the last feature
                fp << ",";               // suffix comma
            }
        }
        if (i < num_points - 1) {  // if not the last row
            fp << "\n";            // start a new line
        }
    }
 
    fp.close();
    return 0;
}

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save_nd_data()

int save_nd_data	(	const char *	fname,
		const std::vector< std::valarray< double > > &	X )

Save a given n-dimensional data martix to file.

Parameters

[in]	fname	filename to save in (gets overwriten without confirmation)
[in]	X	matrix to save

Returns

0 if all ok

-1 if file creation failed

                                                          {
    size_t num_points = X.size();       // number of rows
    size_t num_features = X[0].size();  // number of columns
 
    std::ofstream fp;
    fp.open(fname);
    if (!fp.is_open()) {
        // error with opening file to write
        std::cerr << "Error opening file " << fname << "\n";
        return -1;
    }
 
    // for each point in the array
    for (int i = 0; i < num_points; i++) {
        // for each feature in the array
        for (int j = 0; j < num_features; j++) {
            fp << X[i][j];               // print the feature value
            if (j < num_features - 1) {  // if not the last feature
                fp << ",";               // suffix comma
            }
        }
        if (i < num_points - 1) {  // if not the last row
            fp << "\n";            // start a new line
        }
    }
 
    fp.close();
    return 0;
}

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Variable Documentation

MAX_ITER

constexpr int MAX_ITER = 500

constexpr

Maximum number of iterations to learn