Reading in only first couple lines of input file

I'm trying to create a program that reads in data for 3 separate days and analyzes it. The data file has 72 lines (24 for each day). I only want to read in data for the first day (first 24 lines), but I cannot figure out how to.
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#include <iostream> // Needed for normal cin & cout statements
#include <fstream> // Needed to read or write files on disk
#include <cstdlib> // Needed for exit
#include <cmath> // Needed for certain math functions
#include <string> // Needed to read strings
using namespace std;
int main()
{
// Initializes variables
double Data1, Data2, Data3, Total(0);
int k;

// Opens data file
ifstream infile;
infile.open("data.txt");

if(!infile)
{
cout<<"Unable to open file: Data.txt\n"; // Displays error message if data file cannot be opened
system("pause"); // Pauses command window
exit (0); // Exits program
}
else
{
for(k=1; k<=24; k++) //Counter to read first 24 lines
{
while(infile>>Data1>>Data2>>Data3) // Reads in 3 data items
{
if(Data1 > 1) // Ignores Data1 if it is 1 or 0
Total=Total+Data1; // Adds up Data1 for first 24 lines
}
}
cout<<Total<<endl;
}
system("pause"); //Pauses console window
return (0); // Ends program
}

This:

Code:

---

while (infile >> Data1 >> Data2 >> Data3) // Reads in 3 data items
{
    if (Data1 > 1) // Ignores Data1 if it is 1 or 0
        Total = Total + Data1; // Adds up Data1 for first 24 lines
}

---

should be:

Code:

---

if (infile >> Data1 >> Data2 >> Data3) // Reads in 3 data items
{
    if (Data1 > 1) // Ignores Data1 if it is 1 or 0
        Total += Data1; // Adds up Data1 for first 24 lines
}
else
{
    // report missing data?
    break;
}

---

Notice that I posted in [code][/code] bbcode tags and indented the example code. Next time, please do the same.

EDIT:
Also, try and declare variables near first use. It is bad practice to declare Data1, Data2, Data3, Total and k at the start the main function when you could have declared them before the loop. In fact, you can even declare k in the for loop, i.e.,

Code:

---

for (int k = 0; k < 24; ++k)

---

Likewise, you could have declared Data1, Data2 and Data3 in the body of the for loop, though declaring them just before the loop is acceptable.

Thanks, that worked great. I'll make sure to post the right way next time.

How would I then read the data for the next day (lines 25-48)? I tried the following:

Code:

---

for(int k=1; k<=24; k++)
                  {
                  if(infile>>Data1>>Data2>>Data3)  // Reads in 3 data items
                        {                                           
                        if(sunlight > 1)  // Ignores Data 1 if it is 1 or 0
                            Total+=Data1;    // Adds up Data1 for first 24 lines                           
                        }
   
                  while(k>24 && k<=48)  // Analyzes data for lines 25 to 48
                        Total2=Data1;  // Adds up Data1 for lines 25 to 48
                  }

---

Use another loop, something like

Code:

---

for(int k=25; k<=48; k++)

---

Also, you have to add to 'total' variable, not overwrite its data.

Code:

---

Total2 += Data1;

---

Where would I add the new loop? I tried Adding it after the first for loop, but that did not work.

Basically, the same loop as first one, but change the variable 'Total' to 'Total2'.

Consider using arrays instead of variables like 'Total*' in case you wanna read next 3 days, or even more.

I'm still new to c++. Could you give an example of how to use an array?