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// $Id$ |
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/* |
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Copyright (C) 2017 Peter Johansson |
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This file is part of the yat library, http://dev.thep.lu.se/yat |
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The yat library is free software; you can redistribute it and/or |
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modify it under the terms of the GNU General Public License as |
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published by the Free Software Foundation; either version 3 of the |
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License, or (at your option) any later version. |
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The yat library is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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General Public License for more details. |
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You should have received a copy of the GNU General Public License |
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along with yat. If not, see <http://www.gnu.org/licenses/>. |
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*/ |
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#include <config.h> |
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#include "PoissonFitter.h" |
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#include "yat/utility/DiagonalMatrix.h" |
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#include <cassert> |
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#include <cmath> |
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namespace theplu { |
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namespace yat { |
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namespace regression { |
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namespace detail { |
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PoissonFitter::PoissonFitter(const utility::Matrix& X, |
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const utility::VectorBase& y, |
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utility::Vector& beta, |
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utility::Matrix& covariance) |
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: beta_(beta), covariance_(covariance), X_(X), y_(y) |
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{ |
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init(); |
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size_t n = y_.size(); |
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size_t p = X_.columns(); |
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double olddev = 0; |
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double dev = deviate(); |
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double deltadev = dev - olddev; |
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size_t iteration = 0; |
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while (std::abs(deltadev) > 1e-6 && iteration < 100) { |
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++iteration; |
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utility::DiagonalMatrix W(mu_); |
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// z = eta + (y-mu)/w |
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utility::Vector z(eta_); |
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for (size_t i=0; i<z.size(); ++i) |
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z(i) += (y(i) - mu_(i)) / mu_(i); |
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assert(X_.rows() == n); |
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assert(X_.columns() == p); |
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utility::Matrix I = transpose(X_) * (W * X); |
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inverse_svd(I, covariance_); |
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// avoid matrix * matrix |
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beta_ = covariance_ * (transpose(X_) * (W * z)); |
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assert(X_.columns() == beta_.size()); |
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eta_ = X_ * beta_; |
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for (size_t i=0; i<eta_.size(); ++i) |
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mu_(i) = exp(eta_(i)); |
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olddev = dev; |
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dev = deviate(); |
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deltadev = dev - olddev; |
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} |
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} |
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double PoissonFitter::deviate(void) const |
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{ |
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double sum = 0; |
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for (size_t i=0; i<y_.size(); ++i) { |
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if (y_(i) && mu_(i)) |
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sum += y_(i) * std::log(y_(i) / mu_(i)); |
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} |
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return 2*sum; |
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} |
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void PoissonFitter::init(void) |
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{ |
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mu_ = y_; |
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mu_ += sum(y_)/y_.size(); |
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mu_ *= 0.5; |
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eta_.resize(mu_.size()); |
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for (size_t i=0; i<eta_.size(); ++i) |
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eta_(i) = std::log(mu_(i)); |
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beta_.resize(X_.columns()); |
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covariance_.resize(beta_.size(), beta_.size()); |
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} |
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}}}} |