Datastatistieken

Data opschonen in Java

Dennis Lee

Software Engineer

Maak kennis met je docent!

 

Dennis Lee

 

  • Software engineer bij Amazon
  • Technologie en operations
  • Ph.D. in Elektrotechniek en Computertechniek

 

Foto van de docent

Data opschonen in Java

Waarom schone data telt

 

Title Publish Date Rating Review Count Price
[null] 1/10/23 4.8 165 $30.61
9/13/19 4.8 2,521 $38.00
Clean Code 8/1/08 4.7 5,639 $400.00

 

  • Vuile data: gemiste verkopen, verwarring bij klanten, onbetrouwbare voorspellingen
  • Oplossing: data schoonmaken
Data opschonen in Java

Cursusoverzicht

  1. Beoordeel datakwaliteit

 

1_Ch1_L1_.jpg

Data opschonen in Java

Cursusoverzicht

  1. Beoordeel datakwaliteit
  2. Transformeer data

 

2_Ch1_L1_.jpg

Data opschonen in Java

Cursusoverzicht

  1. Beoordeel datakwaliteit
  2. Transformeer data
  3. Valideer data

 

3_Ch1_L1_.jpg

Data opschonen in Java

Cursusoverzicht

  1. Beoordeel datakwaliteit
  2. Transformeer data
  3. Valideer data
  4. Reinig tabeldata

 

4_Ch1_L1_.jpg

Data opschonen in Java

Onze data structureren

import java.time.LocalDate;

public class BookSalesExample {
    private record BookSales(String title, LocalDate publishDate, 
                             int reviewCount,  double rating, double price) {}}

book.rating() // book is an instance of BookSales
Title Publish Date Rating Review Count Price
Python Crash Course 1/10/23 4.8 165 $30.61
The Pragmatic Programmer 9/13/19 4.8 2,521 $38.00
Clean Code 8/1/08 4.7 5,639 $40.00
Data opschonen in Java

De dataset vullen

import java.time.LocalDate;
import java.util.Arrays;
import java.util.List;

// Create books with title, publishDate, reviewCount, rating, and price
List<BookSales> books = Arrays.asList(
        new BookSales("Python Crash Course", LocalDate.of(2023, 1, 10),
                      165, 4.8, 30.61),
        new BookSales("The Pragmatic Programmer", LocalDate.of(2019, 9, 13),
                      2521, 4.5, 38.00),
        new BookSales("Clean Code", LocalDate.of(2008, 8, 1),
                      5639, 4.7, 40.00));
Data opschonen in Java

Gemiddelde, min, max berekenen

import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;


public class BookSalesExample {
    public static void main(String[] args) {
        // Create stats calculator
        DescriptiveStatistics stats = new DescriptiveStatistics();
        // Add each book's price to stats
        books.forEach(book -> stats.addValue(book.getPrice()));
    }
}
Data opschonen in Java

Voorbeelduitvoer: prijsbereik

System.out.printf("Books analyzed: %d%n", books.size());

Books analyzed: 3

System.out.printf("Average price: $%.2f%n", stats.getMean());

Average price: $36.20

System.out.printf("Price range: $%.2f - $%.2f%n", stats.getMin(), stats.getMax());

Price range: $30.61 - $40.00
Data opschonen in Java

Percentielen berekenen

public class BookSalesExample {
    public static void main(String[] args) {
        // 50th percentile = median
        System.out.printf("Median price: $%.2f%n", stats.getPercentile(50));

        System.out.printf("Normal range: $%.2f - $%.2f%n",
                stats.getPercentile(25), stats.getPercentile(75));
    }
}

Median price: $38.00

Normal range: $30.61 - $40.00
Data opschonen in Java

Statistiek als kwaliteitscontrole

  • Methoden van DescriptiveStatistics
    • .getMean(): gemiddelde prijs
    • .getMin(), .getMax(): prijsbereik
    • .getPercentile(): typische prijzen
  • Vind issues door prijsbereiken te bekijken
  • Voordelen
    • Snelle detectie
    • Schaalbaar naar grote datasets
    • Vervangt handmatige inspectie

Stapels boeken

Data opschonen in Java

Laten we oefenen!

Data opschonen in Java

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