Merge and aggregate datasets



Task

Merge and aggregate two datasets as provided in   .csv   files into a new resulting dataset.

Use the appropriate methods and data structures depending on the programming language.

Use the most common libraries only when built-in functionality is not sufficient.



Note

Either load the data from the   .csv   files or create the required data structures hard-coded.


patients.csv   file contents:

PATIENT_ID,LASTNAME
1001,Hopper
4004,Wirth
3003,Kemeny
2002,Gosling
5005,Kurtz


visits.csv   file contents:

PATIENT_ID,VISIT_DATE,SCORE
2002,2020-09-10,6.8
1001,2020-09-17,5.5
4004,2020-09-24,8.4
2002,2020-10-08,
1001,,6.6
3003,2020-11-12,
4004,2020-11-05,7.0
1001,2020-11-19,5.3



Create a resulting dataset in-memory or output it to screen or file, whichever is appropriate for the programming language at hand.

Merge and group per patient id and last name,   get the maximum visit date,   and get the sum and average of the scores per patient to get the resulting dataset.



Note that the visit date is purposefully provided as ISO format,   so that it could also be processed as text and sorted alphabetically to determine the maximum date.

| PATIENT_ID | LASTNAME | LAST_VISIT |  SCORE_SUM | SCORE_AVG |
| 1001       |  Hopper  | 2020-11-19 |  17.4      | 5.80      |
| 2002       |  Gosling | 2020-10-08 |   6.8      | 6.80      |
| 3003       |  Kemeny  | 2020-11-12 |            |           |
| 4004       |  Wirth   | 2020-11-05 |  15.4      | 7.70      |
| 5005       |  Kurtz   |            |            |           |



Note

This task is aimed in particular at programming languages that are used in data science and data processing, such as F#, Python, R, SPSS, MATLAB etc.



Related tasks

 CSV data manipulation
 CSV to HTML translation
 Read entire file
 Read a file line by line


#include <iostream>
#include <optional>
#include <ranges>
#include <string>
#include <vector>
 
using namespace std;
 
struct Patient
{
    string ID;
    string LastName;
};
 
struct Visit
{
    string PatientID;
    string Date;
    optional<float> Score;
};
 
int main(void) 
{
    auto patients = vector<Patient> {
        {"1001", "Hopper"},
        {"4004", "Wirth"},
        {"3003", "Kemeny"},
        {"2002", "Gosling"},
        {"5005", "Kurtz"}};
 
    auto visits = vector<Visit> {    
        {"2002", "2020-09-10", 6.8},
        {"1001", "2020-09-17", 5.5},
        {"4004", "2020-09-24", 8.4},
        {"2002", "2020-10-08", },
        {"1001", ""          , 6.6},
        {"3003", "2020-11-12", },
        {"4004", "2020-11-05", 7.0},
        {"1001", "2020-11-19", 5.3}};
 
    // sort the patients by ID
    sort(patients.begin(), patients.end(), 
         [](const auto& a, const auto&b){ return a.ID < b.ID;});    
 
    cout << "| PATIENT_ID | LASTNAME | LAST_VISIT | SCORE_SUM | SCORE_AVG |\n";
    for(const auto& patient : patients)
    {
        // loop over all of the patients and determine the fields
        string lastVisit;
        float sum = 0;
        int numScores = 0;
 
        // use C++20 ranges to filter the visits by patients
        auto patientFilter = [&patient](const Visit &v){return v.PatientID == patient.ID;};
        for(const auto& visit : visits | views::filter( patientFilter ))
        {
            if(visit.Score)
            {
                sum += *visit.Score;
                numScores++;
            }
            lastVisit = max(lastVisit, visit.Date);
        }
 
        // format the output
        cout << "|       " << patient.ID << " | ";
        cout.width(8); cout << patient.LastName << " | ";
        cout.width(10); cout << lastVisit << " | ";
        if(numScores > 0)
        {
            cout.width(9); cout << sum << " | ";
            cout.width(9); cout << (sum / float(numScores));
        }
        else cout << "          |          ";
        cout << " |\n";
    }
}