I have a CSV file formatted as below:
1,50,a,46,50,b
2, 20,s,56,30,f
3,35,b,5,67,s
...
How can I turn that to a 2D array so that I could do some calculations?
void Core::parseCSV(){
std::ifstream data("test.csv");
std::string line;
while(std::getline(data,line))
{
std::stringstream lineStream(line);
std::string cell;
while(std::getline(lineStream,cell,','))
{
//not sure how to create the 2d array here
}
}
};
Try this,
void Core::parseCSV()
{
std::ifstream data("test.csv");
std::string line;
std::vector<std::vector<std::string> > parsedCsv;
while(std::getline(data,line))
{
std::stringstream lineStream(line);
std::string cell;
std::vector<std::string> parsedRow;
while(std::getline(lineStream,cell,','))
{
parsedRow.push_back(cell);
}
parsedCsv.push_back(parsedRow);
}
};
NOTE: this will not work if the content of the columns have ,
Following code is working. hope it can help you. It has a CSV file istream_iterator-like class. It is a template so that it can read strings, ints, doubles, etc. Its constructors accept a char delimiter, so that it may be used for more than strictly comma-delimited files. It also has a specialization for strings so that white space characters could be retained.
#include <iostream>
#include <sstream>
#include <fstream>
#include <iterator>
using namespace std;
template <class T>
class csv_istream_iterator: public iterator<input_iterator_tag, T>
{
istream * _input;
char _delim;
string _value;
public:
csv_istream_iterator( char delim = ',' ): _input( 0 ), _delim( delim ) {}
csv_istream_iterator( istream & in, char delim = ',' ): _input( &in ), _delim( delim ) { ++*this; }
const T operator *() const {
istringstream ss( _value );
T value;
ss >> value;
return value;
}
istream & operator ++() {
if( !( getline( *_input, _value, _delim ) ) )
{
_input = 0;
}
return *_input;
}
bool operator !=( const csv_istream_iterator & rhs ) const {
return _input != rhs._input;
}
};
template <>
const string csv_istream_iterator<string>::operator *() const {
return _value;
}
int main( int argc, char * args[] )
{
{ // test for integers
ifstream fin( "data.csv" );
if( fin )
{
copy( csv_istream_iterator<int>( fin ),
csv_istream_iterator<int>(),
ostream_iterator<int>( cout, " " ) );
fin.close();
}
}
cout << endl << "----" << endl;
{ // test for strings
ifstream fin( "data.csv" );
if( fin )
{
copy( csv_istream_iterator<string>( fin ),
csv_istream_iterator<string>(),
ostream_iterator<string>( cout, "|" ) );
fin.close();
}
}
return 0;
}
I would go for something like this (untested, incomplete) and eventually refine operator >>, if you have strings instead of chars, or floats instead of ints.
struct data_t
{
int a ;
int b ;
char c ;
int d ;
int e ;
char f ;
} ;
std::istream &operator>>(std::istream &ist, data_t &data)
{
char comma ;
ist >> data.a >> comma
>> data.b >> comma
>> data.c >> comma
>> data.d >> comma
>> data.e >> comma
>> data.f
;
return ist ;
}
void Core::parseCSV(){
std::ifstream data("test.csv");
std::string line;
std::vector<data_t> datavect ;
while(std::getline(data,line))
{
data_t data ;
std::stringstream lineStream(line);
lineStream >> data ;
datavect.push_back(data) ;
}
};
aandb? Is there some hard-coded mapping to numeric values you could do calculations with? Or should they be ignored? Do you have to remember them to "solve" some matrix system for their values? If you don't want to deal with those issues initially, you could simply read the values into astd::vector<std::vector<std::string>> values;, which you'd put before the firstwhileloop: inside that loop,push_backan emptyvector<std::string>orvalues.resize(values.size() + 1);if you prefer, then push back cell values inside.1: [50,'a'a,46,50,'b'], 2: [2,20,'s',56,30,'f']....