Reading file's columns into array

Question

i'm reading file which has some number of columns each line has different number of columns and they are numerical values of different length, and i have fix number of rows (20) how to put each column in to array?

suppose i have data file like following (there is tab between each column)

20   30      10
22   10       9       3     40 
60    4
30    200   90
33    320    1        22    4

how to put these columns into different array,, that column 1 goes to one arrary and column 2 goes to another. Only column 2 has more than 2 digit values and the rest of columns has 1 or two digit values, and some columns are null too except 1, 2, and 3

int main()
{     
    ifstream infile;
    infile.open("Ewa.dat");

    int c1[20], c2[20], ... c6[20];

    while(!infile.eof()) { 
        //what will be the code here?
        infile >>lines;
        for(int i = 1; i<=lines; i++) {
            infile >> c1[i];     
            infile >> c2[i];
             .
             .
            infile >> c6 [20]; 
        }
    }
}

No, you didn't tag it at all. Someone else edited and added a C tag and then another person corrected the C tag to C++. — Carey Gregory
– Carey Gregory, Commented May 9, 2012 at 18:28

P.P · Accepted Answer · 2012-05-09 18:23:13Z

1

Here's the main idea:

Use a 2D array instead of many 1D arrays.
Read each line using std::string.
Then use: istringstream is(str); which will help parse the string and put into the arrays like this:

while(...) {
    ....
    getline(infile, str);
    istringstream is(str);
    j=0;
    while(is)
        {
            is >> c[i][j];
        }
    i++;
    ....
    }

I'll leave the rest to you.

answered May 9, 2012 at 18:23

P.P

122k20 gold badges193 silver badges251 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

me_newbie Over a year ago

thanks very much KingsIndian for your time and help, it was really helpful

Nate Kohl · Accepted Answer · 2012-05-09 18:35:38Z

1

It might be easier to take advantage of some of some C++ library classes, like std::vector, std::istringstream, and std::string:

#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';
}

answered May 9, 2012 at 18:35

Nate Kohl

36k10 gold badges45 silver badges55 bronze badges

1 Comment

me_newbie Over a year ago

can you fix the problem of garbage values, it is also filling the array for which i don't have any value in the data file?

Collectives™ on Stack Overflow

Reading file's columns into array

2 Answers 2

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related