2021-12-29 11:33:52 +00:00
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/*
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2023-12-11 20:08:57 +00:00
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* Copyright (c) 2015-2024 Sergey Bakhurin
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2021-12-29 11:33:52 +00:00
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* Digital Signal Processing Library [http://dsplib.org]
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*
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* This file is part of libdspl-2.0.
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*
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* is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* DSPL 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
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with Foobar. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "dspl.h"
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#ifdef DOXYGEN_ENGLISH
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/*! ****************************************************************************
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\ingroup ARRAY_GROUP
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2023-12-11 20:08:57 +00:00
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2021-12-29 11:33:52 +00:00
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\brief Function fills a vector with `n` logarithmically spaced elements
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between \f$10^{x_0}\f$ and \f$10^{x_1}\f$.
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Function supports two kinds of filling according to `type` parameter: \n
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Symmetric fill (parameter `type=DSPL_SYMMETRIC`): \n
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\f$x(k) = 10^{x_0} \cdot dx^k\f$, here \f$dx = \sqrt[n-1]{10^{x_1 - x_0}}\f$,
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\f$k = 0 \ldots n-1.\f$
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Periodic fill (parameter `type=DSPL_PERIODIC`): \n
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\f$x(k) = 10^{x_0} \cdot dx^k\f$, here \f$dx = \sqrt[n]{10^{x_1 - x_0}}\f$,
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\f$k = 0 \ldots n-1.\f$ \n
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\param[in] x0
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Start exponent value \f$x_0\f$. \n \n
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\param[in] x1
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End exponent value \f$x_1\f$. \n \n
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\param[in] n
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Number of points `x` (size of vector `x`). \n \n
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\param[in] type
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Fill type: \n
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`DSPL_SYMMETRIC` --- symmetric, \n
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`DSPL_PERIODIC` --- periodic. \n \n
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\param[in,out] x
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Pointer to the output logarithmically spaced vector `x` . \n
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Vector size is `[n x 1]`. \n
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Memory must be allocated. \n \n
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\return
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`RES_OK` if function returns successfully. \n
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Else \ref ERROR_CODE_GROUP "error code".
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\note
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Difference between symmetric and periodic filling we can
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understand from the follow examples. \n
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Example 1. Periodic fill.
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\code{.cpp}
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double x[5];
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logspace(-2, 3, 5, DSPL_PERIODIC, x);
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\endcode
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Values in the vector `x` are:
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\verbatim
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0.01, 0.1, 1, 10, 100
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\endverbatim
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\n \n
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Example 2. Symmetric fill.
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\code{.cpp}
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double x[5];
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logspace(-2, 3, 5, DSPL_SYMMETRIC, x);
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\endcode
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Values in the vector `x` are:
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\verbatim
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0.01 0.178 3.162 56.234 1000
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\endverbatim
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\author Sergey Bakhurin www.dsplib.org
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***************************************************************************** */
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#endif
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#ifdef DOXYGEN_RUSSIAN
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/*! ****************************************************************************
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\ingroup ARRAY_GROUP
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2023-12-11 20:08:57 +00:00
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2021-12-29 11:33:52 +00:00
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\brief Функция заполняет массив значениями логарифмической шкале
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Заполняет массив `x` длиной `n` значениями в диапазоне
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от \f$10^{x_0}\f$ до \f$10^{x_1}\f$. \n
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Функция поддерживает два типа заполнения в соответствии с параметром `type`: \n
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Симметричное заполнение согласно выражению: \n
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\f$x(k) = 10^{x_0} \cdot dx^k\f$, где \f$dx = \sqrt[n-1]{10^{x_1 - x_0}}\f$,
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\f$k = 0 \ldots n-1.\f$
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Периодическое заполнение согласно выражению:
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\f$x(k) = 10^{x_0} \cdot dx^k\f$, где \f$dx = \sqrt[n]{10^{x_1 - x_0}}\f$,
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\f$k = 0 \ldots n-1.\f$ \n
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\param[in] x0
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Начальное значение показателя \f$x_0\f$. \n \n
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\param[in] x1
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Конечное значение показателя \f$x_1\f$. \n \n
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\param[in] n
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Количество точек массива `x`. \n \n
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\param[in] type
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Тип заполнения: \n
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`DSPL_SYMMETRIC` --- симметричное заполнение, \n
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`DSPL_PERIODIC` --- периодическое заполнение. \n \n
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\param[in,out] x
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Указатель на вектор значений в логарифмической шкале. \n
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Размер вектора `[n x 1]`. \n
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Память должна быть выделена. \n \n
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\return
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`RES_OK` --- функция выполнена успешно. \n
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В противном случае \ref ERROR_CODE_GROUP "код ошибки".
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\note
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Отличие периодического и симметричного заполнения можно
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понять из следующих примеров. \n
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Пример 1. Периодическое заполнение.
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\code{.cpp}
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double x[5];
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logspace(-2, 3, 5, DSPL_PERIODIC, x);
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\endcode
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В массиве `x` будут лежать значения:
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\verbatim
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0.01, 0.1, 1, 10, 100
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\endverbatim
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\n \n
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Пример 2. Симметричное заполнение.
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\code{.cpp}
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double x[5];
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logspace(-2, 3, 5, DSPL_SYMMETRIC, x);
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\endcode
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В массиве `x` будут лежать значения:
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\verbatim
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0.01 0.178 3.162 56.234 1000
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\endverbatim
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\author Бахурин Сергей www.dsplib.org
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***************************************************************************** */
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#endif
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int DSPL_API logspace(double x0, double x1, int n, int type, double* x)
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{
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double mx, a, b;
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int k;
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if(n < 2)
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return ERROR_SIZE;
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if(!x)
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return ERROR_PTR;
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a = pow(10.0, x0);
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b = pow(10.0, x1);
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switch (type)
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{
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case DSPL_SYMMETRIC:
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mx = pow(b/a, 1.0/(double)(n-1));
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x[0] = a;
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for(k = 1; k < n; k++)
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x[k] = x[k-1] * mx;
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break;
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case DSPL_PERIODIC:
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mx = pow(b/a, 1.0/(double)n);
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x[0] = a;
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for(k = 1; k < n; k++)
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x[k] = x[k-1] * mx;
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break;
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default:
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return ERROR_SYM_TYPE;
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}
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return RES_OK;
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}
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