C++ Data files, arrays, and calculations assignment - c++

Question

I'm new to C++ and I'm running into an issue on one of my assignments. The goal is to load data from a data file that looks like this.
item number date quantity cost per each
1000 6/1/2018 2 2.18
1001 6/2/2018 3 4.44
1002 6/3/2018 1 15.37
1001 6/4/2018 1 4.18
1003 6/5/2018 7 25.2
Basically I need to do calculations the average item number used for each date using arrays and do some other calculations with the cost. I'm getting really hung up with loading the data from the file and manipulating it for equations. This is what I have so far.
#include <cmath> //for math operations
#include <iostream> //for cout
#include <cstdlib> //for compatibility
#include <fstream>
#include <string>
using namespace std;
int main()
{
string date;
int EOQ, rp;
int count;
int itemnum[][];
double quantity[][];
double cost[][];
ifstream myfile;
string filename;
cout << "Data File: " << endl;
cin >> filename; // user enters filename
myfile.open(filename.c_str());
if(myfile.is_open())
{
cout << "file opened" << endl;
string head;
while(getline(myfile, head))
{
break; // so header won't interfere with data
}
while(!myfile.eof())
{ // do this until reaching the end of file
int x,y;
myfile >> itemnum[x][y] >> date >> quantity[x][y] >> cost[x][y];
cout << "The numbers are:" << endl;
for(count = 0; count < y; count++)
{
cout << itemnum[x][y] << endl;
break;
}
//cout << "Item: Reorder Point: EOQ: " << endl;
//cout << itemnum << " " << rp << " " << EOQ << endl;
break;
}
}
else
{
cout << "" << endl; //in case of user error
cerr << "FILE NOT FOUND" << endl;
}
cout << endl;
cout << "---------------------------------------------" << endl;
cout << " End of Assignment A8" << endl;
cout << "---------------------------------------------" << endl;
cout << endl;
system("pause");
return 0;
I haven't started working with the equations yet since I still can't get the file loaded in a simple array!!!
Thank you!
Link for data file : https://drive.google.com/file/d/1QtAC1bu518PEnk4rXyIXFZw3AYD6OBAv/view?usp=sharing

Answer 1

When working on these kinds of problems I like to break these down into the parts related to parsing. I'm using some of the standard libraries to do some of the work for me. I also created a couple of structures to help keep the information of the data organized. As for your date, I could of left that as a single std::string but I chose to break the date down into three individual types themselves and store them into a data structure just to show the capabilities of one of the functions that is involved with parsing.
What I prefer doing is to get either a single line of data from a file and save that to a string, or get the entire contents of a file and save that either to a large buffer or a vector of strings, unless if I'm handling specific type of code where that is not applicable such as parsing a wav file. Then close the file handle as I'm done reading from it! Then after I have all of the information I need, instead of trying to parse the file directly while it is opened I'd rather parse a string as it is easier to parse. Then after parsing the string we can populate our data types that we need.
I had to modify your data file slightly to accommodate for the extra white spaces so I saved your file as a text file with only a single white space between each data type within a single line of text. I also did not include the first line (header) information as I just omitted it completely. However this should still act as a guide of how to design a good work flow for an application that has good readability, reusability, try to keep it portable and as generic as possible. Now, what you have been waiting for; the demonstration of my version of your code:
#include <string>
#include <sstream>
#include <iostream>
#include <fstream>
#include <exception>
struct Date {
int month;
int day;
int year;
Date() = default;
Date( int monthIn, int dayIn, int yearIn ) :
month( monthIn ),
day( dayIn ),
year( yearIn )
{}
};
struct DataSheetItem {
int itemNumber;
Date date;
int quantity;
double costPerEach;
DataSheetItem() = default;
DataSheetItem( int itemNumberIn, Date& dateIn, int quantityIn, double costPerEachIn ) :
itemNumber( itemNumberIn ),
date( dateIn ),
quantity( quantityIn ),
costPerEach( costPerEachIn )
{}
};
std::vector<std::string> splitString( const std::string& s, char delimiter ) {
std::vector<std::string> tokens;
std::string token;
std::istringstream tokenStream( s );
while( std::getline( tokenStream, token, delimiter ) ) {
tokens.push_back( token );
}
return tokens;
}
void getDataFromFile( const char* filename, std::vector<std::string>& output ) {
std::ifstream file( filename );
if( !file ) {
std::stringstream stream;
stream << "failed to open file " << filename << '\n';
throw std::runtime_error( stream.str() );
}
std::string line;
while( std::getline( file, line ) ) {
if ( line.size() > 0 )
output.push_back( line );
}
file.close();
}
DataSheetItem parseDataSheet( std::string& line ) {
std::vector<std::string> tokens = splitString( line, ' ' ); // First parse with delimeter of a " "
int itemNumber = std::stoi( tokens[0] );
std::vector<std::string> dateInfo = splitString( tokens[1], '/' );
int month = std::stoi( dateInfo[0] );
int day = std::stoi( dateInfo[1] );
int year = std::stoi( dateInfo[2] );
Date date( month, day, year );
int quantity = std::stoi( tokens[2] );
double cost = std::stod( tokens[3] );
return DataSheetItem( itemNumber, date, quantity, cost );
}
void generateDataSheets( std::vector<std::string>& lines, std::vector<DataSheetItem>& dataSheets ) {
for( auto& l : lines ) {
dataSheets.push_back( parseDataSheet( l ) );
}
}
int main() {
try {
std::vector<std::string> fileConents;
getDataSheetItemsFromFile( "test.txt", fileContents );
std::vector<DataSheetItem> data;
generateDataSheets( fileConents, data );
// test to see if info is correct
for( auto& d : data ) {
std::cout << "Item #: " << d.itemNumber << " Date: "
<< d.date.month << "/" << d.date.day << "/" << d.date.year
<< " Quantity: " << d.quantity << " Cost: " << d.costPerEach << '\n';
}
} catch( const std::runtime_error& e ) {
std::cerr << e.what() << '\n';
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
NOTE This will not work with how your file currently is; this does not account for the first line of text (header information) and this does not account for any extra white spaces in between the data fields. If you add a single line of text when opening the file and read in a single line and just ignore it, then perform the loop to get all strings to add to vector to return back; your vectors will have the information in it but they will not be at the correct index locations of the vector because of all the extra white spaces. This is something you need to be aware of! Other than that; this is how I would basically design a program or application to parse data. This is by all means not 100% full proof and may not even be 100% bug free, but from a quick glance and running it through my debugger a few times it does appear to be without any noticeable bugs. There could also be some room for improvements for runtime efficiency, etc. but this is just a generalization of basic parsing.