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  1. #1
    Join Date
    Mar 2011

    Post C++ using fstream to calculate average and standard deviation

    Hey, My first time using the forums.
    I have comments in my code to kind of explain what's going on but basically my main problem is it is not letting my close a file and then reopen it.(I FIGURED THIS OUT)
    so now it works very well (I had to make a few little adjustments because I messed up some of the input things and little "off by one" errors)

    My only problem left is that it does not write to the file that a calculation error occurred.
    This is a minor thing but if you have any ideas I would appreciate them.

    Thanks for any help.

    //p365 num. 4
    //calculate average and  standard deviation of a specified file and repeat as needed
    //possible logic error location are marked by the phrase ERROR HERE
    //it doesnt tell file that an error occured
    #include <iostream>
    #include <fstream>
    #include <cstdlib> //for key word - exit
    #include <cmath> // for keyword - sqrt
    using namespace std;
    void avgcalc(ifstream& receive, double& average);
    //ifstream has been opened, ready to take double input
    //output the average using call be reference
    void stddevcalc(ifstream& receive, double average, double& standarddeviation);
    //ifstream has been opened, ready to take input. Average has been calculated
    //output standard deviation using call by reference
    int main ()
        ifstream receive;
        ofstream deliver;
        char yorn; //for yes or no answer to repeat calculations
        int abcd=0;
        cout << "AVERAGE AND STANDARD DEVIATION\n\n"; //title
             double standarddev=0, avg=0, abc=0; //declare the variables to be changed by call by reference, and also abc. abc is used so that the first if statement is only run after the first time it fails
             char fileget[22], filegive[22]="RESULTS.txt", pause; // set variable for file to be calculated and file to be sent to. I use a dummy char variable because I am running in an IDE and it keeps the output on the screen 
                  if(abc > 0) //so error message is output to screen after the first file is not found or there is an error
                       cout << "receive/fileget/first open " << fileget << " - FAILED to OPEN\n";
                  cout << "File name: "; //so the user can specify which file to use for calculations
                  cin >> fileget;
                  abc++; //as stated, this is to control error output
             }while(receive.fail()); //allows user to re-input the file name until he gets it right 
             cout << "receive ifstream has been opened for first calculation\n";
                  deliver.open(filegive, ios::app); //it is set so that it can be appended so that multiple calculations can be done and the user history is kept
                  if (deliver.fail())
                       cout << "deliver/filegive/first open - FAILED to OPEN\n";
                       cin >> pause;
             cout << "deliver ofstream has been opened\n";
             avgcalc(receive, avg);     //average calculation here ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             deliver << "--- For File " << fileget << " ---\nAVG: " << avg << endl; //output the average results to the file
             cout << "receive ifstream has been closed\n";
             receive.open(fileget); //ifstream is closed and re-opened so that the numbers can be read through again by the next function
                  cout << "receive/fileget/second open " << fileget << " - FAILED to OPEN\n";
                  deliver << "Standard Deviation Calculation ERROR\n\n"; //this will output to the file to show that an error occured ERROR HERE
                  cin >> pause;
             cout << "receive ifstream has been opened for second calculation\n";
             stddevcalc(receive, avg, standarddev);        //standard deviation calculation here ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             deliver << "STANDARD DEV: " << standarddev << endl << endl; //standard deviation is added to the file here
             cout << "receive ifstream has been closed\n";
             cout << "Calculations Complete and Sent to " << filegive << "\n\nAgain?\n"; //prompt for another loop
             cin >> yorn;
         }while((yorn != 'n')&&(yorn != 'N'));
     return 0;   
    void avgcalc(ifstream& receive, double& average)
         double number, total=0, count=0;
         while(receive >> number) // to keep the loop going while there is data left in the file and get next number in file
              total+=number; // add number to total
              count++; //increment count
         average = (total / count); //calculate average
    void stddevcalc(ifstream& receive, double average, double& standarddeviation)
         double number, add=0, count=0, sqr=0, sub=0;
         while(receive >> number)
              sub = number - average; //first step of calculating standard deviation
              sqr = sub*sub; //second step of calculating standard deviation. square the first step
              add+=sqr; // third step. add the squared terms up
         standarddeviation = sqrt(add/count); //find the average of the squared terms and square root it --> standard deviation
    Last edited by wsad597; March 8th, 2011 at 06:43 PM. Reason: the formating was improper. This should be better. and the second edit was to refine the question

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