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#include "mp.h"

#include <cassert>
#include <cmath>

double mp::stress(const arma::mat &Dp, const arma::mat &Dq)
{
    assert(Dp.n_rows == Dp.n_cols);
    assert(Dq.n_rows == Dq.n_cols);
    assert(Dp.n_rows == Dq.n_rows);

    arma::uword n = Dp.n_rows;
    double sigma = 0, s = 0;
    for (arma::uword i = 0; i < n; i++)
        for (arma::uword j = i + 1; j < n; j++) {
            double delta = Dp(i, j);
            double d     = Dq(i, j);
            sigma += (delta - d) * (delta - d) / delta;
            s += delta;
        }

    return sigma / s;
}

arma::vec mp::klDivergence(const arma::mat &P, const arma::mat &Q)
{
    arma::vec diver(P.n_rows);
    mp::klDivergence(P, Q, diver);
    return diver;
}

void mp::klDivergence(const arma::mat &P, const arma::mat &Q, arma::vec diver)
{
    assert(P.n_rows == P.n_cols);
    assert(Q.n_rows == Q.n_cols);
    assert(P.n_rows == Q.n_cols);
    assert(diver.n_elem == P.n_rows);

    arma::uword n = P.n_rows;
    for (arma::uword i = 0; i < n; i++)
        diver(i) = klDivergence(P.row(i), Q.row(i));
}

double mp::klDivergence(const arma::rowvec &pi, const arma::rowvec &qi)
{
    return arma::accu(removeJ % (pi % arma::log(pi / qi)));
}

arma::mat mp::d2p(const arma::mat &D, const arma::vec &sigmas)
{
    arma::mat P(D.n_rows, D.n_cols);
    mp::relevance(D, sigmas, P);
    return P;
}

void mp::d2p(const arma::mat &D, const arma::vec &sigmas, arma::mat &P)
{
    /*
     * WARNING: assumes D and sigmas are already squared
     */

    assert(D.n_rows == D.n_cols);
    assert(P.n_rows == P.n_cols);
    assert(D.n_rows == P.n_rows);

    arma::uword n = D.n_rows;
    for (arma::uword i = 0; i < n; i++) {
        double den = -1; // k == i must be skipped
        for (arma::uword k = 0; k < n; k++)
            den += exp(-D(i, k) / sigmas(i));

        for (arma::uword j = 0; j < n; j++)
            P(i, j) = exp(-D(i, j) / sigmas(i)) / den;
    }
}