mjhjmtu

I am trying to write a program that will read the highest and lowest voltage along with its associated amp and time. I am able to find the max, but I am getting all zeros for the minimum value. I need help. Please and thank you.

Sample of txt file:

Time Volt Ampere
0.0001 9.77667 0.147408
0.00015 9.76583 0.147525
0.0002 9.76833 0.147692
0.00025 9.75833 0.147442
0.0003 9.76833 0.147192
0.00035 9.78167 0.1473
0.0004 9.76667 0.147317
0.00045 9.765 0.14715
0.0005 9.75667 0.147
0.00055 9.765 0.14695
0.0006 9.77 0.1471
0.00065 9.7675 0.147417
0.0007 9.7725 0.147417
0.00075 9.755 0.14735
0.0008 9.765 0.147725
0.00085 9.76583 0.147783

Expected Min Output:

Time = 0.00075 Volt = 9.755 Ampere = 0.14735

Expected Max Output:

Time= 0.00035 Volt = 9.78167 Ampere = 0.1473

int main(void)

//Declare Variables
string a, b, c;

double time, volt, ampere;
double maxVolt = 0, maxTime, maxAmpere;
double minVolt = 10, minTime, minAmpere;

//Read from the Volts.txt file
ifstream myFile("D:\tabit\Documents\Volts.txt");

//Check if the file can be opened
if (myFile.is_open())

 while (myFile >> a >> b >> c)
 
 time = atof(a.c_str());
 volt = atof(b.c_str());
 ampere = atof(c.c_str());

 if (volt >= maxVolt)
 
 maxTime = time;
 maxVolt = volt;
 maxAmpere = ampere;
 
 if (volt < minVolt)
 
 minTime = time;
 minVolt = volt;
 minAmpere = ampere;
 
 
 //Close the file
 myFile.close();

//Give error message if the file cannot be opened
else return(1);

//Display the Maximum results
cout << "Max Volt: " << maxVolt << endl;
cout << "Max Time: " << maxTime << endl;
cout << "Max Ampere: " << maxAmpere << endl;

//Display the Minimum results
cout << "Min Volt: " << minVolt << endl;
cout << "Min Time: " << minTime << endl;
cout << "Min Ampere: " << minAmpere << endl;

return 0;

The value of atof("Volt") is zero. The corresponding values of atof("Time") and atof("Ampere") are also zero, which gives you the minimum values of zero you observed.

You need to skip the first line of the file. Adding this before the while loop would work:

myFile.ignore(80, 'n');

Use std::numeric_limits<std::streamsize>::max() instead of 80 for a more correct (but verbose) limit of characters to skip before the new line character.

After you add the skipping of the first line, you no longer need the a, b & c variables and atof() calls; you can read the values directly:

while (myFile >> time >> volt >> ampere)

Your code is missing the headers you need - at least <fstream> and <iostream>. It also seems that there's a using namespace std; lurking somewhere; that's a bad practice that can subtly break your code, so I recommend that you explicitly qualify the names you use from it (std is intentionally a very short name, to save typing).

In C++, we can declare int main() - that's a prototype, unlike in C, where we need to write int main(void). The latter is certainly foreign-looking in C++.

It's probably clearer to return early if the file opening failed:

if (!myFile) 
 std::cerr << "Couldn't open input file";
 return 1;

I'm a little uncomfortable with the compiled-in filename to read from - this makes the program quite inflexible. Either provide the name as a command-line argument, or simply read from standard input so the program can read from any file or from a pipeline.

There's little point closing the input stream if we ignore the result - the stream's destructor will do that for us, so just let it go out of scope.

Be warned that std::endl includes a flush of the output stream - it's better to just write 'n' as line terminator (the stream will be flushed at program exit).