C++ program to read a csv matrix and print the transpose - c++

Question

I currently have a C++ program to read in a matrix of values (type double) and print out the transpose, how can I alter my code so that it can read in csv files rather than spaced matrix text?
I also need to write out the transposed matrix to another file after calculating it, what would be the simplest way of doing this?
int readMatrix(const string & s, vector<double> & v);
void import_csv_matrix(const char* filename_matrix, vector <double> & v, int& rows, int& columns);
int main() {
vector<double> v;
int rows = 0;
int columns = 0;
import_csv_matrix("filename.csv", v, rows, columns);
return 0;
}
int readMatrix (const string & s, vector<double> & v) {
istringstream is(s);
double n;
while (is >> n) {
v.push_back(n);
}
return v.size();
}
void import_csv_matrix(const char* filename_matrix, vector<double>& v, int& rows, int& columns) {
ifstream data_File;
string line;
data_File.open(filename_matrix);
if (data_File.is_open()) {
int i = 0;
getline(data_File, line);
columns = readMatrix(line, v);
for (i = 1; i < 100000; i++) {
if ( !getline(data_File, line) > 0) break;
readMatrix(line, v);
}
rows = i;
data_File.close();
}
cout << "Transpose:" << endl;
for (int i = 0; i < columns; i++) {
for (int j = 0; j < rows; j++) {
cout << v[i + j*columns] << "\t";
}
cout << endl;
}
}

Answer 1

I assume you mean that the rows are still line separated but the elements within rows are comma separated. Then all you need to do is modify the readMatrix function to handle those commas. The following code should work.
int readMatrix(const string& s, vector<double>& v) {
char comma = ',';
istringstream is{s};
for (double temp = 0.0; is >> temp; v.push_back(temp)) {
is >> comma;
if (comma != ',') break; \\ a formatting error has occurred
}
return v.size();
}