How can i set precision while write a column with double data to .csv file?

[QINZHAOYU]

Hi, how can i set precision while write a column with double data to .csv file?

[d99kris]

Hi @QINZHAOYU - there's currently no support for specifying precision per column (we can maybe consider adding..) however one can control all double conversions to string. This conversion is used for all SetCell, SetColumn, SetRow calls. If you're working on an existing CSV file/stream, we can Get and Set just one column, and thus have only it affected. Example setting fixed precision of 2 decimal places:

#include <iostream>
#include <vector>
#include "rapidcsv.h"

namespace rapidcsv
{
  template<>
  void Converter<double>::ToStr(const double& pVal, std::string& pStr) const
  {
    std::ostringstream out;
    out << std::fixed << std::setprecision(2) << pVal;
    pStr = out.str();
  }
}

int main()
{
  const std::string& csv =
    "Date,Open,High,Low,Close,Volume,Adj Close\n"
    "2017-02-24,64.529999,64.800003,64.139999,64.620003,21705200,64.620003\n"
    "2017-02-23,64.419998,64.730003,64.190002,64.620003,20235200,64.620003\n"
    "2017-02-22,64.330002,64.389999,64.050003,64.360001,19259700,64.360001\n"
    "2017-02-21,64.610001,64.949997,64.449997,64.489998,19384900,64.489998\n"
    "2017-02-17,64.470001,64.690002,64.300003,64.620003,21234600,64.620003\n"
  ;

  std::stringstream instream(csv);
  rapidcsv::Document doc(instream);

  std::vector<double> column = doc.GetColumn<double>("Open");
  doc.SetColumn<double>("Open", column);

  std::stringstream outstream;
  doc.Save(outstream);

  std::cout << outstream.str();
}

Expected output:

Date,Open,High,Low,Close,Volume,"Adj Close"
2017-02-24,64.53,64.800003,64.139999,64.620003,21705200,64.620003
2017-02-23,64.42,64.730003,64.190002,64.620003,20235200,64.620003
2017-02-22,64.33,64.389999,64.050003,64.360001,19259700,64.360001
2017-02-21,64.61,64.949997,64.449997,64.489998,19384900,64.489998
2017-02-17,64.47,64.690002,64.300003,64.620003,21234600,64.620003