Help extracting specific data from text file

wariner · #1 23-Apr-2005, 18:16

I am very new to C++ and I have a project involving integration totals.

Please could someone help explain to me how to extract specific data out of a text file:

The way the project works is that I have to take specific data (in this case, acceleration and time values) out of a text file which has been provided. I then need to apply a trapezoidal Riemann sum to the data in order to get velocity and then displacement.

I have got the function for the Riemann sum worked out, all I need help with is how to get the data from the provided file.

It is given in the form:

time1 x-acceleration1 y-acceleration1
time2 x-acceleration2 y-acceleration2
time3 x-acceleration3 y-acceleration3

and is around 7000 lines of that, all numeric.

What I would like to know is, how do I extract the data (and presumably save it to a variable) such as time 1, then time 2 etc. It is all separated by three spaces as shown. I attached a copy of the file, the columns are [time, x-acc, y-acc, x-disp, y-disp]

I would really appreciate if anyone could show me how to pull out the specific data, and then use it in a calculation by way of storing it or using it directly.

Much appreciated

wariner · #2 23-Apr-2005, 18:28

It didn't seem to attach the file last time, so I try again... But it doesn't seem to have worked.

nkhambal · #3 23-Apr-2005, 19:16

Hi,

Welcome to GIDForums.

Pls read this tutorial. It also has an example to to extract data from file using file I/O.

Thanks,

Dave Sinkula · #4 23-Apr-2005, 19:19

Some ideas:

CPP / C++ / C Code:

#include <iostream>
#include <fstream>
#include <vector>

struct data
{
   double time, x_acc, y_acc, x_disp, y_disp;
};

int main()
{
   std::ifstream file("0406268A_data.txt");
   std::vector<data> info;
   data element;
   while ( file >> element.time >> element.x_acc >> element.y_acc
                >> element.x_disp >> element.y_disp )
   {
      info.push_back(element);
   }
   // Example of doing something with the data.
   for (std::vector<data>::size_type i = 0; i < info.size(); ++i)
   {
      std::cout << info[i].time  << ' '
                << info[i].x_acc << ' '
                << info[i].y_acc << std::endl;
   }
   return 0;
}

wariner · #5 24-Apr-2005, 03:14

Thanks so much for the assistance, it really helped me to understand and made my life easier. That tutorial looks great, I'm gonna give it a look now, so thanks to nkhambal.

Much appreciated, Dave Sinkula. The code was grande, it was more helpful than any of my lecturers!

I suppose all I need to do now is apply the formulae to the data, and output it to a CSV file, which should be fine. I guess the text file uploaded after all. I think it didn't work the first time, because I tried to upload from Konqueror, and then in Firefox it seemed to have worked.

Thanks again.

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Help extracting specific data from text file

augment

Many thanks