[C++] Need help with win32 program

I need to graph 3 points based on the linear or quadratic equation and I can't get my head around how to graph the points. It will work fine if you put points in that are in sequence like 2 3 4 but not 2 4 5 any help is greatly appreciated below is the source from microsoft visual studio 2008

Code:

// program002.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <cstdio>
#include <cmath>

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{

	int iNumOfDataPoints, iEquation;
	double mx, my;


	//linear or quadratic if the user enters 0 or any other number the program assums quadratic
	cout << "Choose an equation: Enter 1 for Linear and 0 for quadratic (default is quadratic)" << endl;
	cin >> iEquation;


	//ask user how many data points
	cout<<"Please enter your number from lowest to highest."<<endl;
	cout << "How many data points would you like to plot (max 3)?" << endl;
	cin >> iNumOfDataPoints;
	
	double iDataX[4], iDataY[4];
	
	for(int c=1;c<=iNumOfDataPoints;c++)
	{
		cout << "Enter data point(x) ";
		cout <<	c << endl;
		cin >> iDataX[c];

		if(iDataX[c]<=0)
		{
			cout << "Data point must be positive number. " << endl;
			return 0;
		}

		//now lets get the y values
		//linear
		if(iEquation==1)
		{
			iDataY[c]= 2*iDataX[c] + 4;
		}
		else //quadratic
		{
			iDataY[c]= pow(iDataX[c],2) + 4*iDataX[c]+2;
		}
	}

	cout << endl;
	for(int c=1;c<=iNumOfDataPoints;c++)
	{
		cout << iDataY[c] << endl;
	}
	
cout << endl;
cout << endl;
	//find largest value
	
	mx=std::max(iDataX[1],iDataX[2]);
	mx=std::max(mx,iDataX[3]);
	double mx2=mx;
	
	

	my=std::max(iDataY[1],iDataY[2]);
	my=std::max(my,iDataY[3]);

	

//graph
	int z=iNumOfDataPoints;

	for(my;my!=0;my--)
	{
		cout<<"|";
		if(my==iDataY[z])
		{
				if(mx==iDataX[z])
				{
					int n=1;
					while(n<mx)
					{
						cout<<" ";
						n++;
					}
					cout<<"*"<<endl;
					z--;
				}
				else
				{
					cout<<endl;
				}
				mx--;
		}
		else
		{
			cout<<endl;
		}
	}
	

	for(int f=0;f<=mx2;f++)
	{
		cout << "-";
	}
	cout << endl;
	


	return 0;
}

 

Just change
if(mx==iDataX[z])
to
mx=iDataX[z];
and lose the else clause.

You don't need an if at this point because if(my==iDataY[z]) already removes all cases where there isn't a * to plot. So all you need to do within this if is to look up the value of iDataX[z] and draw the * in the appropriate place.

 

You also don't need the mx--. It was this that was making it "work" when the entered values were consecutive. Consequently you also don't need mx2 as mx doesn't change over the output loop.

 

Just a small correction to xpi0t0s's analysis of your code. mx does change during the output loop because you are assigning to it (in the fixed version). So you do still need mx2.

By the way, you should get used to using zero-based array subscripting, since that is the C/C++ way.

 

Thank you works perfectly now