filters.h

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/* +---------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)               |
   |                          http://www.mrpt.org/                             |
   |                                                                           |
   | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file        |
   | See: http://www.mrpt.org/Authors - All rights reserved.                   |
   | Released under BSD License. See details in http://www.mrpt.org/License    |
   +---------------------------------------------------------------------------+ */
#pragma once

#include <mrpt/base/link_pragmas.h>
#include <cstdlib>
#include <cmath>

namespace mrpt
{
        namespace math
        {

                /** @addtogroup filtering_grp Filtering algorithms
                  * \ingroup mrpt_base_grp
                  *  @{ */

                /** 1-order low-pass IIR filter. 
                  * Discrete time equation: `y[k]=alpha*y[k-1]+(1-alpha)*x[k]`.
                  * With: x[k] input, y[k] output, alpha a parameter in [0,1]
                  */
                struct BASE_IMPEXP LowPassFilter_IIR1
                {
                        LowPassFilter_IIR1(double alpha = 0.5, double y_k_minus_1 = .0);
                        double filter(double x); //!< Processes one input sample, updates the filter state and return the filtered value.
                        double getLastOutput() const;
                        double alpha; //!< See equation in LowPassFilter_IIR1
                private:
                        double m_y_km1;
                };

                /** @} */  // end grouping filtering_grp
        } // end NS
} // end NS