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#ifndef _theplu_yat_regression_linear_ |
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#define _theplu_yat_regression_linear_ |
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// $Id$ |
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/* |
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Copyright (C) 2004, 2005, 2006 Jari Häkkinen, Peter Johansson |
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Copyright (C) 2007 Peter Johansson |
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Copyright (C) 2008 Jari Häkkinen, Peter Johansson |
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Copyright (C) 2010 Peter Johansson |
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This file is part of the yat library, http://dev.thep.lu.se/yat |
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|
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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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|
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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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|
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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 "OneDimensional.h" |
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#include <cmath> |
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|
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namespace theplu { |
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namespace yat { |
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namespace utility { |
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class VectorBase; |
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} |
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namespace regression { |
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/** |
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@brief linear regression. |
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|
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Data are modeled as \f$ y_i = \alpha + \beta (x_i-m_x) + |
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\epsilon_i \f$. |
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*/ |
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class Linear : public OneDimensional |
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{ |
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|
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public: |
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/// |
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/// @brief The default constructor |
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/// |
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Linear(void); |
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|
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/// |
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/// @brief The destructor |
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/// |
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virtual ~Linear(void); |
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|
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/** |
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The parameter \f$ \alpha \f$ is estimated as \f$ |
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\frac{1}{n}\sum y_i \f$ |
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|
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@return the parameter \f$ \alpha \f$ |
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*/ |
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double alpha(void) const; |
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|
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/** |
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The variance is estimated as \f$ \frac{s^2}{n} |
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\f$ where \f$ s^2 = \frac{\sum \epsilon^2}{n-2} \f$ |
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|
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@return variance of parameter \f$ \alpha \f$ |
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*/ |
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double alpha_var(void) const; |
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|
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/** |
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The parameter \f$ \beta \f$ is estimated as \f$ |
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\frac{\textrm{Cov}(x,y)}{\textrm{Var}(x)} \f$ |
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|
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@return the parameter \f$ \beta \f$ |
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*/ |
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double beta(void) const; |
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/** |
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The variance is estimated as \f$ \frac{s^2}{\sum |
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(x-m_x)^2} \f$ where \f$ s^2 = \frac{\sum \epsilon^2}{n-2} \f$ |
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|
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@return variance of parameter \f$ \beta \f$ |
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*/ |
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double beta_var(void) const; |
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/** |
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Model is fitted by minimizing \f$ \sum{(y_i - \alpha - \beta |
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(x-m_x))^2} \f$. By construction \f$ \alpha \f$ and \f$ \beta \f$ |
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are independent. |
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*/ |
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void fit(const utility::VectorBase& x, const utility::VectorBase& y) ; |
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/// |
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/// @return \f$ \alpha + \beta x \f$ |
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/// |
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double predict(const double x) const; |
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|
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/** |
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\f$ \frac{\sum \epsilon_i^2}{N-2} \f$ |
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|
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@return variance of residuals |
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*/ |
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double s2(void) const; |
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/** |
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The error of the model is estimated as \f$ |
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\textrm{alpha\_err}^2+\textrm{beta\_err}^2*(x-m_x)*(x-m_x)\f$ |
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|
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@return estimated error of model in @a x |
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*/ |
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double standard_error2(const double x) const; |
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private: |
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/// |
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/// Copy Constructor. (not implemented) |
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/// |
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Linear(const Linear&); |
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double alpha_; |
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double alpha_var_; |
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double beta_; |
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double beta_var_; |
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}; |
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|
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}}} // of namespaces regression, yat, and theplu |
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|
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#endif |