C++读取.txt并保存csv

要读取的 .txt 文件类似这种data.txt：

-83.635047	 -248.884343	 -15.649366
-83.237317	 -248.651216	 -15.458514
-82.838610	 -248.419124	 -15.266673
-82.438903	 -248.188020	 -15.075844
-82.039185	 -247.956894	 -14.886015
-81.638502	 -247.727802	 -14.695220
-81.236808	 -247.499677	 -14.506436
-80.835137	 -247.272574	 -14.316676
-80.432466	 -247.046460	 -14.127926
-80.028807	 -246.821357	 -13.939188
-79.624149	 -246.597244	 -13.751461
-79.219502	 -246.374130	 -13.563757
-78.813867	 -246.153006	 -13.377087
-78.407233	 -245.931893	 -13.190406
-77.999622	 -245.712792	 -13.003759
-77.592011	 -245.494667	 -12.818134
-77.182412	 -245.277567	 -12.632510

以上数据文本有如下特点，每行数据个数相同，数据之间采用空格隔开，读取该数据文件的方式有逐词读取、逐行读取。

#include <iostream>
#include <sstream>
#include <fstream>
using namespace std;

int main()
{
    
    
    // 逐词读取，按照空格进行分隔
    ifstream fin("data.txt");
    string s;
    while(fin>>s) 
    {
    
    
        cout<<s<<endl;
    }
    fin.close();
    s.clear();
    
    // 逐行读取，按照每行结束的回车区分
    fin.open("data.txt");
    while(getline(fin,s)) 
    {
    
    
        cout<<s<<endl;
    }
    fin.close();
    s.clear();
    return 0;
}

		// 逐词读取，按照空格进行分隔
	ifstream fin("bottom.txt");
	string s;
	while (fin >> s)
	{
    
    
		cout << s << endl;
	}
	fin.close();
	s.clear();


	// 逐行读取，按照每行结束的回车区分
	fin.open("bottom.txt");
	while (getline(fin, s))
	{
    
    
		cout << s << endl;
	}
	fin.close();
	s.clear();

逐行读取操作数据不灵活，逐词读取数据体量又太大，那么自然想到先逐行，再从每一行中采用逐词读取的方式提取到感兴趣的数据。

	ifstream fin;
	istringstream iss;
	string s;
	double t;
	vector<double> tube;
	int count = 0;
	// 逐行读取，将每一行数据读取到字符串 s 中
	fin.open("bottom.txt");
	while (getline(fin, s))
	{
    
    
		iss.clear();
		iss.str(s);
		// 逐词读取，遍历每一行中的每个词 t
		while (iss >> t)
		{
    
    
			cout << t << " ";
		}
		cout << endl;
	}

按照上述方式，就可以提取到你感兴趣的数据，比如抽取该data.txt文件的第一二三列数据，并存放到bottom.csv文件中（方便 Matlab 绘制曲线用）：

	ifstream fin;
	ofstream outFile;           // 2、创建流对象
	istringstream iss;
	string s;
	double t;
	vector<double> tube_x;
	vector<double> tube_y;
	vector<double> tube_z;
	int count = 0;
	// 按行读取，将每一行数据读取到字符串 s 中
	fin.open("bottom.txt");
	while (getline(fin, s))
	{
    
    
		iss.clear();
		iss.str(s);
		// 逐词读取，操作/提取 你感兴趣的数据
		while (!iss.eof())
		{
    
    
			iss >> t;
			count += 1;
			if (count % 3 == 1)
			{
    
    
				tube_x.push_back(t);
			}
			if (count % 3 == 2)
			{
    
    
				tube_y.push_back(t);
			}
			if (count % 3 == 0)
			{
    
    
				tube_z.push_back(t);
			}
		}
		count = 0;
	}
	int num = tube_x.size();
	cout << "num=" << num << endl;
	for (int j = 0; j < num; j++)
	{
    
    
		cout << "tube_x:" << tube_x[j] << "        " << "tube_y:" << tube_y[j] << "        " << "tube_z:" << tube_z[j] << endl;
		outFile.open("bottom.csv", ios::app);
		outFile << tube_x[j] << "," << tube_y[j] << "," << tube_z[j] << "\n";
		outFile.close();
	}