很多数据资料的格式类似这样：
1,-2085738.7757,5503702.8697,2892977.6829
2,-2071267.5135,5520926.7235,2883341.8135
3,-2079412.5535,5512450.8800,2879771.2119
4,-2093693.1744,5511218.2651,2869861.8947
5,-2113681.5062,5491864.0382,2896934.4852
6,-2100573.2849,5496675.0138,2894377.6030
其中数据按照N(点号），X，Y，Z（三维坐标）排序。
这里提供一种C++读入"N,X,Y,Z"格式文本文件到Eigen3 Matrix的方法，以及对应的同格式输出方法
`
#pragma once
#include
#include
#include
#include
#include
#include
#include
using namespace std;
using namespace Eigen;
// 字符串分割
void SplitString(const std::string& s, std::vector& v, const std::string& c)
{
std::string::size_type pos1, pos2;
pos2 = s.find(c);
pos1 = 0;
while (std::string::npos != pos2)
{
v.push_back(s.substr(pos1, pos2 - pos1));
pos1 = pos2 + c.size();
pos2 = s.find(c, pos1);
}
if (pos1 != s.length())
v.push_back(s.substr(pos1));
}
// 读入相应格式的xyz文件
void ReadXYZFile(string filepath, MatrixXd& origin_data)
{
ifstream infile;
infile.open(filepath);
cout << "Reading XYZ File: " << filepath << endl;
if (!infile.is_open())
{
cout << "File Cannot Open" << endl;
exit(1);
}
int r = 0; // 逐行加载数据
char buffer[100];
while (!infile.eof())
{
// getline只能读成char*，
// 而SplitString只能切割string,
// 而atof又只能转化char*到double
infile.getline(buffer, 100);
// cout << buffer << endl;
string line = buffer;
if (line == "")
{
continue;
}
vector vector_data;
SplitString(line, vector_data, ",");
for (int c = 0; c < origin_data.cols(); c++)
{
origin_data(r, c) = atof(vector_data[c].c_str());
}
r++;
}
return;
}
// 将矩阵按读入的相同格式保存至相应路径
void WriteXYZFile(string filepath, MatrixXd& trans_data)
{
ofstream outfile;
outfile.open(filepath, ios::out | ios::trunc);
for (int r = 0; r < trans_data.rows(); r++)
{
for (int c = 0; c < trans_data.cols(); c++)
{
if (c < trans_data.cols() - 1)
{
outfile << trans_data(r, c) << ',';
}
if (c == trans_data.cols() - 1)
{
outfile << trans_data(r, c);
}
}
outfile << endl;
}
cout << "Write XYZ File: " << filepath << endl;
outfile.close();
return;
}