June 2009
Beginner to intermediate
428 pages
9h 48m
German
Content preview from Data Mining mit Microsoft SQL Server
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3.3. Fehlende und ungenaue Werte
Dieser Abschnitt zeigt Möglichkeiten zum Umgang mit fehlenden und ungenauen Werten auf.
3.3.1. Umgang mit fehlenden Werten
Für fehlende Werte wird in der Welt der relationalen Datenbanken NULL vergeben. Einige Miningverfahren ignorieren solche Attribute. In vielen Fällen existieren jedoch unterschiedliche Gründe, welche dazu führen, dass ein Attribut auf NULL gesetzt wird. Ein Wert könnte beispielsweise NULL sein, da dieser nicht bekannt oder umstritten ist, da eine interviewte Person darüber keine Auskunft geben wollte, da der Wert aufgrund eines Fehlers nicht gemessen werden konnte oder da ein Experiment abgebrochen werden musste, bevor es zur Messung des Wertes kam. In diesen Fällen kann es sinnvoll sein, ...
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