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/* ************************************************************** * C++ Mathematical Expression Toolkit Library * * * * ExprTk GNUPlot Example * * Author: Arash Partow (1999-2024) * * URL: https://www.partow.net/programming/exprtk/index.html * * * * Copyright notice: * * Free use of the Mathematical Expression Toolkit Library is * * permitted under the guidelines and in accordance with the * * most current version of the MIT License. * * https://www.opensource.org/licenses/MIT * * SPDX-License-Identifier: MIT * * * ************************************************************** */ #include #include #include #include #include #include "exprtk.hpp" class exprtk_gnuplot_fx { public: exprtk_gnuplot_fx() : min_x_(0.0) , max_x_(0.0) , min_y_(0.0) , max_y_(0.0) {} exprtk_gnuplot_fx& set_title(const std::string& title) { title_ = title; return *this; } exprtk_gnuplot_fx& set_domain(const double min_x, const double max_x) { min_x_ = min_x; max_x_ = max_x; return *this; } exprtk_gnuplot_fx& set_expression(const std::string& expression) { expression_ = expression; return *this; } bool plot() { if (!generate_data()) return false; else return generate_gp_script(); } private: bool generate_gp_script() { std::ofstream stream("plot.gp"); if (!stream) { return false; } stream << "set term png\n"; stream << "set output 'plot.png'\n"; stream << "set xrange[" << min_x_ << ":" << max_x_ <<"]\n"; stream << "set yrange[" << min_y_ << ":" << max_y_ <<"]\n"; stream << "set xzeroaxis\n"; stream << "set yzeroaxis\n"; stream << "plot 'data.dat' using 1:2:(1.0) smooth unique title '" << title_ <<"'\n"; return true; } bool generate_data() { typedef exprtk::symbol_table symbol_table_t; typedef exprtk::expression expression_t; typedef exprtk::parser parser_t; double x = 0.0; symbol_table_t symbol_table; symbol_table.add_constants(); symbol_table.add_variable("x",x); expression_t expression; expression.register_symbol_table(symbol_table); parser_t parser; if (!parser.compile(expression_,expression)) { return false; } std::ofstream stream("data.dat"); if (!stream) { return false; } min_y_ = +std::numeric_limits::max(); max_y_ = -std::numeric_limits::max(); stream << std::setprecision(10); const double increment = std::min(0.00005,std::abs(max_x_ - min_x_) / 1000.0); for (x = min_x_; x <= max_x_; x += increment) { const double y = expression.value(); if (y < min_y_) min_y_ = y; else if (y > max_y_) max_y_ = y; stream << x << "\t" << y << "\n"; } const double diff_y = std::abs(max_y_ - min_y_); const double perc7_5 = diff_y * 0.075; //7.5% min_y_ -= perc7_5; max_y_ += perc7_5; return true; } std::string title_; std::string expression_; double min_x_; double max_x_; double min_y_; double max_y_; }; int main() { exprtk_gnuplot_fx plotter; plotter .set_expression("clamp(-1.0,sin(2 * pi * x) + cos(x / 2 * pi),+1.0)") .set_domain(-5,+5) .set_title("ExprTk GNUPlot Example"); plotter.plot(); return 0; } /* Build and Run: 1. c++ -ansi -pedantic-errors -Wall -Wextra -Werror -Wno-long-long -O3 -DNDEBUG -o exprtk_gnuplot exprtk_gnuplot.cpp -lstdc++ 2. ./exprtk_gnuplot 3. gnuplot plot.gp */