Reading file into array

[me_newbie]

Hi Guys!

i'm reading a file which has 20 rows and random number of columns, i want to put them in array/vector which i did but the problem is that array is filling a cell with a garbage value at location where i don't have a value in the data file.

suppose i have data file like following (there is tab between each column and each row has different number of columns)

20   30      10
22   10      9       3      40 
60    4
30   200     90
33   320             22

here is my code

#include <vector>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>

int main() {
     std::vector<std::vector<int> > allData;

     std::ifstream fin("data.dat");
     std::string line;
    
    while (std::getline(fin, line)) {      // for each line
            std::vector<int> lineData;           // create a new row
            int val;
            std::istringstream lineStream(line); 
    
           while (lineStream >> val) {          // for each value in line
                   lineData.push_back(val);           // add to the current row
           }
         
           allData.push_back(lineData);         // add row to allData
    }

    //std::cout << "row 0 contains " << allData[0].size() << " columns\n";
    //std::cout << "row 0, column 1 is " << allData[0][1] << '\n';
}

your help will be appreciated

Regards,
Ewa

[Philip Nicoletti]

Are you accessing "cells that don't have a value" ?

The following is how you would loop thru this structure:

    for (int i=0; i<allData.size(); ++i)
    {
        for (int j=0; j<allData[i].size(); ++j)
        {
            cout << allData[i][j] << " ";
        }
        cout << "\n";
    }

[me_newbie]

Are you accessing "cells that don't have a value" ?

The following is how you would loop thru this structure:

    for (int i=0; i<allData.size(); ++i)
    {
        for (int j=0; j<allData[i].size(); ++j)
        {
            cout << allData[i][j] << " ";
        }
        cout << "\n";
    }

Thanks for reply, i modified your code to suit my purpose and now i want to access a specific column in a specific row. how to do it? because i want to read and analyze the 3rd column values.

int currentPosition=1;
        
    for (int i=0;i<allData.size();i++){
        for (int j =0;j<allData[i].size();j++){
            if (allData[i][0]==currentPosition){    
                for (;j<allData[i].size();j++){
              	  cout << "" << allData[i][j] << '\t';        
                }        
             cout << "" << endl;
            }
                
        }
            
    }
}

Thanks in advance

[Philip Nicoletti]

Is this what you want ?

    int column = 2; // 0-based (so 3rd column)

    for (int i=0; i<allData.size(); ++i)
    {
        cout << "row = " << i << " : ";

        if (column < allData[i].size() )
        {
            cout << allData[i][column] << "\n";
        }
        else
        {
            cout << "column does not exist for this row\n";
        }
        cout << "\n";
    }

[me_newbie]

Is this what you want ?

    int column = 2; // 0-based (so 3rd column)

    for (int i=0; i<allData.size(); ++i)
    {
        cout << "row = " << i << " : ";

        if (column < allData[i].size() )
        {
            cout << allData[i][column] << "\n";
        }
        else
        {
            cout << "column does not exist for this row\n";
        }
        cout << "\n";
    }

Thank Philip Nicoletti your help was very fruitful, i modified it for my purpose

thumb up to you

Regards,

Ewa