Reading data from text file into an array

[dogwood705]

Hi, I am new to C++ and am getting stuck with just reading in data from a text file into an array. I have looked at lots of examples online, but can't find one that matches what I am trying to do.

The data consists of two variables, date and price, and looks like the following:
01/01/2010,37.58
01/02/2010,29.10
01/03/2010,24.59
01/04/2010,22.24
01/05/2010,32.90
.
.
.

For now, I am using just January data (31 records), but in general I will be using a file for a year (daily data), but with missing days.

I am attaching my code. My problem is that I am putting all of the first line into the string variable (first szTempDate and then pds.szDate). I don't know how to get it to read only the date and then how to get the price into pds.dPrice. I didn't put anything here to try to read the price because of the string problem. Also, if there is a simpler way to read the file into the array than what I have, I would love to know how.

My second question has to do with not knowing in general how many records are in the file without looking at it and I have to do this for a lot of years. Is there a way to create an array that has only the number of objects that correspond to the number of data records in the file and then have the program tell me how many that is?
Thanks very much!!

// reading a text file
#include <cstdio>
#include <cstdlib>
#include <iostream>

#include <fstream>
#include <string>
using namespace std;

//PriceData - Defines a class that stores the date and price data
class PriceData
{
public:
	std::string szDate;
	double dPrice; //contains the daily price 
	void setDate(std::string& str)
	{
		szDate = str;
	}
	void setPrice(double& p)
	{
		dPrice = p;
	}
};

// Allocate 31 objects of class PriceData
PriceData pds[31];
// Creat temporary variables for holding the data as it is read from the file
string szTempDate;
double dTempPrice;


//displayData - This function outputs the indexed data set
void displayData(PriceData& pds)
{
	cout << pds.szDate;
	cout << " ";
	cout << pds.dPrice;
	cout << endl;
}

int main (int nArg, char* pszArgs[])
{
  ifstream myfile ("Prices.txt");
  if (myfile.is_open())
  {  
	//while (!myfile.eof())
		//{
			for(int i = 0; i <31; i++)
			{
				getline(myfile,szTempDate);
				pds[i].setDate(szTempDate);
				displayData(pds[i]);
							}
		//}
	myfile.close();
  }

  else cout << "Unable to open file"; 

  system("PAUSE");
  return 0;
//}

}

[daviddoria]

You should read a line at a time and use this:
http://programmingexamples.net/index.php?title=CPP/Strings/Split

You should have a Data class and overload the input operator to handle parsing the dates (with the /'s etc)

[dogwood705]

Thanks for the link to the example about splitting strings. But I'm still stuck on how I make the second item into a double type, not a string.

Also, can you please explain why I should overload the input operator.

Thanks!

[mrnutty]

1) Easiest way, copy ALL of the data into notepad
2) On the notepad, click Edit->replace. Now replace all ',' with ' '
3) Now you can read in the date as a string, and the price as a double

[dogwood705]

Thanks for the suggestion to change the file in notepad. I understand how that would work. Unfortunately, I am working on this as part of an assignment for a class and have to deal with the file as is.

[mrnutty]

Thanks for the suggestion to change the file in notepad. I understand how that would work. Unfortunately, I am working on this as part of an assignment for a class and have to deal with the file as is.

Try something like this then :

string data = "01/01/2010,37.58";
	string::size_type pos = data.find_first_of(',');
	string date = data.substr(0,pos); //contains "01/01/2010"
	string strPrice = data.substr(pos + 1); // contains "37.58"
	float price = atof( strPrice.c_str() ); //contains 37.58

[dogwood705]

I solved the problem by combining two of the suggestions. I split the string into two strings and then converted the second string to a double. Thanks for the suggestons.

[dart57]

Dogwood -

Could you please post your solution? I have a similar problem to solve.

thx

[dogwood705]

By the time you posted your request, I had already added a lot of code to my program to do other things and I don't have the time to separate it all out. Please see the comment I made earlier about following the suggestions to split the string and then convert the second one.