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100 lines
4.0 KiB
C++
100 lines
4.0 KiB
C++
/*
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**************************************************************
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* C++ Mathematical Expression Toolkit Library *
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* *
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* Simple Example 13 *
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* Author: Arash Partow (1999-2017) *
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* URL: http://www.partow.net/programming/exprtk/index.html *
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* *
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* Copyright notice: *
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* Free use of the Mathematical Expression Toolkit Library is *
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* permitted under the guidelines and in accordance with the *
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* most current version of the MIT License. *
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* http://www.opensource.org/licenses/MIT *
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* *
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**************************************************************
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*/
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#include <cstdio>
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#include <cstdlib>
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#include <ctime>
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#include <string>
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#include "exprtk.hpp"
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template <typename T>
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void savitzky_golay_filter()
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{
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typedef exprtk::symbol_table<T> symbol_table_t;
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typedef exprtk::expression<T> expression_t;
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typedef exprtk::parser<T> parser_t;
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std::string sgfilter_program =
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" var weight[9] := "
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" { "
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" -21, 14, 39, "
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" 54, 59, 54, "
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" 39, 14, -21 "
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" }; "
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" "
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" if (v_in[] >= weight[]) "
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" { "
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" var lower_bound := trunc(weight[] / 2); "
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" var upper_bound := v_in[] - lower_bound; "
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" "
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" v_out := 0; "
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" "
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" for (var i := lower_bound; i < upper_bound; i += 1) "
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" { "
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" for (var j := -lower_bound; j <= lower_bound; j += 1) "
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" { "
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" v_out[i] += weight[j + lower_bound] * v_in[i + j]; "
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" }; "
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" }; "
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" "
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" v_out /= sum(weight); "
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" } ";
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const std::size_t n = 1024;
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std::vector<T> v_in;
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std::vector<T> v_out;
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const T pi = T(3.141592653589793238462643383279502);
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srand(static_cast<unsigned int>(time(0)));
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// Generate a signal with noise.
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for (T t = T(-5); t <= T(+5); t += T(10.0 / n))
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{
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T noise = T(0.5 * (rand() / (RAND_MAX + 1.0) - 0.5));
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v_in.push_back(sin(2.0 * pi * t) + noise);
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}
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v_out.resize(v_in.size());
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symbol_table_t symbol_table;
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symbol_table.add_vector("v_in" , v_in);
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symbol_table.add_vector("v_out",v_out);
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expression_t expression;
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expression.register_symbol_table(symbol_table);
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parser_t parser;
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parser.compile(sgfilter_program,expression);
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expression.value();
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for (std::size_t i = 0; i < v_out.size(); ++i)
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{
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printf("%10.6f\t%10.6f\n",v_in[i],v_out[i]);
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}
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}
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int main()
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{
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savitzky_golay_filter<double>();
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return 0;
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}
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