C++ C++；，使用GNUPLOT绘制矩阵

我有一个矩阵MDATA（100,20）。我想画出这列的5个数字。 e、 g.，图1：第1-4列

图2：第6-10列

图1：第12-15列，依此类推。 我用GnUpTror和C++（GnUpTrimiSo.h）。

我试过了

gp << "plot" << gp.file1d(MDATA.col(1)) << "with lines title 'Column_1',"
        << gp.file1d(MDATA.col(2)) << "with lines title 'Column_2',"
        << gp.file1d(MDATA.col(3)) << "with lines title 'Column_3',"
        << gp.file1d(MDATA.col(4)) << "with lines title 'Column_4'" << endl;

gp
ofstream outFile;
ifstream inFile;
    

    outFile.open("out.txt", ios::out);
    outFile << "\"plot\"";
    for (int i = 1; i < 5; i++) {
        outFile <<  "<<gp.file1d(MDATA.col(" <<to_string(i)<<")) << "<<"\""<<"with lines title 'Column_"<<to_string(i)<<"',"<<"\"";
    }
    //outFile << "<<endl";
    outFile.close();

    inFile.open("out.txt", ios::in);

    std::string content((std::istreambuf_iterator<char>(inFile)),
        (std::istreambuf_iterator<char>()));
    inFile.close();
       // gp << content << endl; // ERROR: invalid command
        
 gp << content.cstr() << endl; ////process exited with code -1073741515