Whats wrong with my code?

[Yagada]

I cannot seem to figure the error in my code. Basically, its suppose to take 2 arrays and sort them then print them out. Any help will be greatly appreciated.

This is my header file:

#include<iostream>
#include <iomanip>
#include <string>
using namespace std;

class SnowData
{
private:
	int dates[7];
	double inches[7];
	string monthName;
	int startdate;
public:
	SnowData(string, int, double[]);
	double getAverage();
	void print();
	void sortByDate();
	void sortByInches();

};

My .cpp file:

#include "SnowData.h"


double SnowData::getAverage()
{
		int sum = 0;
		int average = 0;
		for (int i = 0; i < 7; ++i)
			sum += inches[i];
			average = sum / 7;

		return average;
}


void SnowData::print()
{

	cout << "Snow Report for the month of " << monthName << endl;

	cout << "Date                    Snow" << endl;
	cout << "--------------------------------" << endl;
	sortByDate();

	cout << "Snow Report for the month of " << monthName << endl;

	cout << "Date                    Snow" << endl;
	cout << "--------------------------------" << endl;
	sortByInches();
}


SnowData::SnowData(string _monthName, int _startdate, double _inches[])
{
	for(int i = 0; i < 7; i++)
		inches[i] = _inches[i];
	for(int i = 0; i < 7; i++)
		dates[i] = _startdate + i;
}


void sortByDate(int dates[], int size)
{
	int startScan, minIndex, minValue;

	for (startScan = 0; startScan < (size - 1); startScan++)
	{
		minIndex = startScan;
		minValue = dates[startScan];
		for (int index = startScan + 1; index < size; index++)
		{
			if (dates[index] < minValue)
			{
				minValue = dates[index];
				minIndex = index;
			}
		}
		dates[minIndex] = dates[startScan];
		dates[startScan] = minValue;
	}
	
}

void sortByInches(double inches[], int size)
{
	int startScan, minIndex, minValue;

	for (startScan = 0; startScan < (size - 1); startScan++)
	{
		minIndex = startScan;
		minValue = inches[startScan];
		for (int index = startScan + 1; index < size; index++)
		{
			if (inches[index] < minValue)
			{
				minValue = inches[index];
				minIndex = index;
			}
		}
		inches[minIndex] = inches[startScan];
		inches[startScan] = minValue;
	}
	
}

And my tester .cpp:

#include<iostream>
#include <iomanip>
#include <string>
using namespace std;
#include "SnowData.h"

int main()
{
	double snow_inches[7] = { 5.6, 7.7, 2.4, 1.9, 1.5, 4.5, 3.4 };

	SnowData snow_data("January", 12, snow_inches);

	snow_data.sortByDate();
	cout << "---------- Sorted by Date -------\n";
	snow_data.print();

	snow_data.sortByInches();
	cout << "--------- Sorted by Inches ---------\n";
	snow_data.print();

	cout << "Average snowfall = " << setprecision(2)
		<< snow_data.getAverage() << " inches\n";

	return 0;
}