C++ Determining empty cells from reading in data

Question

I'm reading in data from a csv file that has some columns ending before others, i.e.:

0.01 0.02 0.01
0.02      0.02

And I'm trying to figure out how to catch these empty locations and what to do with them. My current code looks like this:

#include <iostream>
#include <fstream>
#include <sstream>
int main(){

//Code that reads in the data, determines number of rows & columns

//Set up array the size of all the cells (including empty):
double *ary = new double[cols*rows]; //Array of pointers
double var;
std::string s;
int i = 0, j = 0;

while(getline(data,line))
{
    std::istringstream iss(line);    //Each line in a string
    while(iss >> var)                //Send cell data to placeholder
    {
        ary[i*cols+j] = var;
        j+=1;
    }
    i+=1;
}

How can I determine if the cell is empty? I want to convert these to "NaN" somehow. Thank you!

Answer 1

You can do something like follows. Get the inputs, line by line and using (std::getline(sstr, word, ' ')) you can set the deliminator to ' ' and the rest is checking weather the scanned word is empty or not.

If it's empty, we will set it to NaN(only once).

Input:
0.01 0.02 0.01
0.02      0.02
0.04      0.08

Here is the output:

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

int main()
{
    std::fstream file("myfile.txt");
    std::vector<std::string> vec;

    if(file.is_open())
    {
        std::string line;
        bool Skip = true;

        while(std::getline(file, line))
        {
            std::stringstream sstr(line);
            std::string word;

            while (std::getline(sstr, word, ' '))
            {
                if(!word.empty())
                    vec.emplace_back(word);

                else if(word.empty() && Skip)
                {
                    vec.emplace_back("NaN");
                    Skip = false;
                }
            }
            Skip = true;
        }
        file.close();
    }

    for(size_t i = 0; i < vec.size(); ++i)
    {
        std::cout << vec[i] << " ";
        if((i+1)%3 ==0) std::cout << std::endl;
    }
    return 0;
}