如何读取CSV文件并分配给Eigen Matrix？

问题描述

我试图读一个大的cvs文件到Eigen Matrix，下面的代码发现有问题，它不能检测\\\
在cvs文件中的每一行，以在矩阵中创建多行。 （它用单行读取整个文件）。不知道代码有什么问题。任何人都可以在这里建议？
我也在寻找一个有效的方式来读取csv文件与10k的行和1k的cols。不那么确定下面的代码将是最好的有效方法？非常感谢您的评论。

I try to read a large cvs file into Eigen Matrix, below the code found having problem where it can not detect each line of \n in cvs file to create multiple rows in the matrix. (It read entire file with single row). Not sure what's wrong with the code. Can anyone suggest here?Im also looking for a effective way to read csv file with 10k of rows and 1k of cols. Not so sure the code below will be the best effective way? Very appreciated with your comment.

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <fstream>
#include <istream> //DataFile.fail()  function
#include <vector>
#include <set>
#include <string>
using namespace std;


#include <Eigen/Core>
#include <Eigen/Dense>
using namespace Eigen;

 void readCSV(istream &input, vector< vector<string> > &output)
{
    int a = 0;
    int b = 0;

    string csvLine;
    // read every line from the stream
    while( std::getline(input, csvLine) )
    {

        istringstream csvStream(csvLine);
        vector<string> csvColumn;
        MatrixXd mv;
        string csvElement;
        // read every element from the line that is seperated by commas
        // and put it into the vector or strings
        while( getline(csvStream, csvElement, ' ') )
        {
            csvColumn.push_back(csvElement);
            //mv.push_back(csvElement);
            b++;
        }
        output.push_back(csvColumn);
        a++;
    }
    cout << "a : " << a << " b : " << b << endl;   //a doen't detect '\n'
}

int main(int argc, char* argv[])
{

    cout<< "ELM" << endl;
    //Testing to load dataset from file.
    fstream file("Sample3.csv", ios::in);
    if(!file.is_open())
    {
        cout << "File not found!\n";
        return 1;
    }
    MatrixXd m(3,1000);
    // typedef to save typing for the following object
    typedef vector< vector<string> > csvVector;
    csvVector csvData;

    readCSV(file, csvData);
    // print out read data to prove reading worked
    for(csvVector::iterator i = csvData.begin(); i != csvData.end(); ++i)
    {
        for(vector<string>::iterator j = i->begin(); j != i->end(); ++j)
        {
           m(i,j) = *j;
           cout << *j << ", ";
        }
        cout << "\n";
    }
}

我还将附加一个示例cvs文件。

推荐答案

正确的csv文件：

std::ifstream indata;

indata.open(filename);

std::string                line;
while (getline(indata, line))
{
    std::stringstream          lineStream(line);
    std::string                cell;

    while (std::getline(lineStream, cell, ','))
    {
        //Process cell
    }
}

编辑此外，由于您的csv中有数字，请务必使用 std :: stod 或等效转换一次。

Also, since your csv is full of numbers, make sure to use std::stod or the equivalent conversion once you expect to treat them as such.

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