劳动节闲来无事，写了一天程序，just for fun.

看，这是C++调用Matlab画图的一段程序。暂时不想多解释了，有兴趣的话，看看下面的代码吧。

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
#include <ctime>
using namespace std;


#include <Eigen/Eigen>
#include <engine.h>

class MatArray
{
public:
    MatArray() : _data(NULL){}
    MatArray(size_t irows, size_t icols){
        resize(irows, icols);
    }
    MatArray(const MatArray &obj){
        if (obj._data){
            _data = mxCreateDoubleMatrix(obj.rows(), obj.cols(), mxREAL);
            memcpy(this->ptr(), obj.ptr(), sizeof(double)*rows()*cols());
        }
        else{
            _data = NULL;
        }
    }
    ~MatArray(){ mxDestroyArray(_data); _data = NULL; }

    inline size_t rows() const { return _data? mxGetM(_data):0; }
    inline size_t cols() const { return _data? mxGetN(_data):0; }
    inline double* ptr() const { return _data? mxGetPr(_data):NULL; }

    bool resize(size_t irows, size_t icols){
        if (!_data){
            _data = mxCreateDoubleMatrix(irows, icols, mxREAL);
            return (_data != NULL);
        }
        if (rows() == irows || cols() == icols){
            return true;
        }
        mxDestroyArray(_data); 
        _data = mxCreateDoubleMatrix(irows, icols, mxREAL);
        return (_data != NULL);
    }

    int put(Engine *ep, const char* var_name){
        return engPutVariable(ep, var_name, _data);
    }

    template<class EigenMat=Eigen::MatrixXf>
    void copy_from_eigen(const EigenMat &emat){
        if (emat.rows()*emat.cols() == 0){
            mxDestroyArray(_data); _data = NULL;            
        }
        resize(emat.rows(), emat.cols());
        for (int c = 0; c < emat.cols(); c++){
            for (int r = 0; r < emat.rows(); r++){
                (*this)[r + c*emat.rows()] = emat(r, c);
            }
        }
    }
    inline double& operator[](int i){
        return ptr()[i];
    }

private:
    mxArray *_data;
};

class Matlab
{
private:
    Matlab(const Matlab &obj){}
public:
    Matlab(){
         _engine = engOpen(NULL);
         if (!_engine){
             cerr << "failed to open MATLAB engine!" << endl;
         }
         else{
             cout << "MATLAB has been started successfully!" << endl;
         }       
    }
    ~Matlab(){
        // if you are testing algorithm, you are encouraged to keep the line below bing committed.
        //engClose(_engine); _engine = NULL;
    }

    template<class TMatX = Eigen::MatrixXf, class TMatY = Eigen::MatrixXf>
    int plot(const TMatX &X, const TMatY &Y, string line_spec = "", int figure_id = 1, bool hold_on = false){
        MatArray MX, MY, ID;
        MX.copy_from_eigen(X); MX.put(_engine, "MX");
        MY.copy_from_eigen(Y); MY.put(_engine, "MY");
        ID.resize(1, 1); ID[0] = figure_id; ID.put(_engine, "ID");

        string plot_code = " figure(ID); plot(MX, MY";
        if (line_spec != ""){
            plot_code = plot_code + "," + line_spec;
        }
        plot_code += ");";
        plot_code += hold_on ? "hold on;" : "hold off;";

        return engEvalString(_engine, plot_code.c_str());
    }   

    int exec(string cmd){
        return engEvalString(_engine, cmd.c_str());
    }

private:
    Engine *_engine;
};

string rndcolor(){
    string color = "[";
    color += to_string((rand() % 256) / 255.) + ",";
    color += to_string((rand() % 256) / 255.) + ",";
    color += to_string((rand() % 256) / 255.) + "]";
    return color;
}

int main(int argc, char** argv){
    Eigen::MatrixXf data;

    srand((unsigned int)time(0));
    data = data.Random(1000, 2);

    Matlab mateng;
    //mateng.exec("clear all; close all;");
    mateng.plot(data.col(0), data.col(1), string("'s',") + "'MarkerEdgeColor'," + rndcolor() + ",'MarkerFaceColor'," + rndcolor() + ", 'MarkerSize', 5", 1, true);

    return EXIT_SUCCESS;
}

执行一下！看看结果！