c++ - 如何按升序对输入文件中的数字进行排序，并找到它们的范围和中位数？

Question

我正在开发一个程序，它从一个 txt 文件中读取信息，然后计算它的均值、中位数、众数、范围、标准差和方差。如何将输入文件中的数字按升序排序并找到这些值的中位数和范围？输入 .txt 文件中的所有数字都是随机排列的。

#include <iostream>
#include <cmath>
#include <string>
#include <fstream>
#include <iomanip>
#include <sstream>



using namespace std;

int main()
{

// Define Variables
    string null;
    int input=0, counter=0, numAscend=0;
    float datSum, datMean;
    const string SPCHAR= " ";

// File Algorithms
    // Input File and Output File
        ifstream fin; // <--- Reading from this File
        ofstream myfile; // <--- Writing to this File

    // Output File Computing
        // Place the directory to the file you want to write to here.
myfile.open("/home/anomaly/Desktop/finaldata.txt");

        // What is being wrote to the output file.
myfile << "Writing this to a file.\n";


fin.open("/home/anomaly/Desktop/arsenic.txt");


// Main Operation of Program

        fin >> input;
    getline(fin, null);
    while (fin.good())
    {
        datSum += input;
        fin >> input;
        getline(fin, null);
        counter++;
    }

    // Data Configurations
        datMean = (datSum / counter);






    cout << "There are " << counter << " item(s)" << endl;
    cout << setprecision(1) << input << endl;
    cout << fixed << setprecision(2) << SPCHAR << "The mean is " << datMean << SPCHAR << SPCHAR << SPCHAR << SPCHAR << SPCHAR << SPCHAR << " The variance is " << endl;
    cout << fixed << setprecision(2) << SPCHAR << SPCHAR << "The median is " << datSum << SPCHAR << SPCHAR << SPCHAR << " The Stand. Deviation is " << endl;
    cout << fixed << setprecision(2) << SPCHAR << SPCHAR << SPCHAR << "The mode is " << datSum << SPCHAR << SPCHAR << SPCHAR << SPCHAR << SPCHAR << SPCHAR << " The range is " << endl;






    myfile << setprecision(2) << datSum << endl;


return 0;
}

Answer 1

我建议您从文件中读取所有值并将它们放入 std::vector 中以简化计算。

这是一种可以通过一些示例来完成的方法，这些示例说明如何对平均值和中值进行排序、求和和计算。

#include <algorithm> // std::sort
#include <fstream>
#include <iostream>
#include <iterator>  // std::istream_iterator, std::back_inserter
#include <numeric>   // std::accumulate
#include <string>
#include <vector>    // std::vector

// a function to read all values of a certain type (T) from a stream
// and put them in a vector
template<typename T>
std::vector<T> extract_data_from_stream(std::istream& is) {
    std::vector<T> retval;

    // copy all values from the stream and put them in a vector
    std::copy(std::istream_iterator<T>(is), std::istream_iterator<T>(),
              std::back_inserter(retval));

    // not at end-of-file, extraction ran into problems 
    if(is.eof() == false)
        throw std::runtime_error("extraction failed");

    return retval;
}

// a wrapper function to open a file and call the above function
template<typename T>
std::vector<T> extract_data_from_file(const std::string& filename) {
    // open the file
    std::ifstream fin(filename);

    // if the file was opened ok, extract all data and return it
    if(fin) return extract_data_from_stream<T>(fin);

    // else throw
    throw std::runtime_error("Could not open " + filename + " for reading");
}

int main() {
    try {
        // get all int:s from a file as a std::vector<int>
        auto data = extract_data_from_file<int>("/home/anomaly/Desktop/arsenic.txt");

        // sort the data
        std::sort(data.begin(), data.end());

        // print the data
        std::copy(data.begin(), data.end(),
                  std::ostream_iterator<int>(std::cout, " "));
        std::cout << "\n";

        // sum of the data
        int datSum = std::accumulate(data.begin(), data.end(), 0);

        std::cout << "number of values: " << data.size() << "\n";
        std::cout << "sum:              " << datSum << "\n";

        if(data.size()) { // mean and median must have data
            // get the mean value
            float datMean =
                static_cast<float>(datSum) / static_cast<float>(data.size());

            // find/calculate the median value
            float datMedian;
            size_t mid = data.size() / 2;

            if(data.size() % 2) // odd number of values
                datMedian = static_cast<float>(data[mid]);
            else                // even number of values
                datMedian = static_cast<float>(data[mid - 1] + data[mid]) / 2.f;

            std::cout << "mean:             " << datMean << "\n";
            std::cout << "median:           " << datMedian << "\n";
        }
    } catch(const std::exception& ex) {
        std::cerr << ex.what() << "\n";
    }
}