August 2022
Beginner to intermediate
436 pages
9h 43m
Korean
Content preview from SQL로 시작하는 데이터 분석
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341
6
장
이상 탐지
면 해당 데이터는 삭제하는 편이 좋습니다. 대용량 데이터에서는 레코드 몇 개 정도는 삭제해
도 분석 결과에 전혀 영향이 없지만, 만약 매우 극단적인 아웃라이어 값 때문에 완전히 다른 결
과가 도출될 우려가 있다면 해당 데이터를 삭제하는 편이 좋습니다.
앞서
earthquakes
데이터셋에서 지진 규모 값 중에 수백 개의 –
9
.
99
와 수십 개의 -
9
가 포함
돼 있음을 확인했습니다. 이 값들은 일반적인 지진 규모 값에 비해 극단적으로 작은 값이므로
잘못 입력했거나 (실제 지진 규모를 알 수 없어서 ) 임의로 입력한 값으로 의심됩니다.
WHERE
절을 사용해 이렇게 극단적으로 작은 값을 간단히 제거해봅시다.
SELECT
time
, mag,
type
FROM
earthquakes
WHERE
mag
not
in
(-9,-9.99)
;
time mag type
------------------- ---- ----------
... ... ...
2019-08-11 03:25:39 1.8 earthquake
2019-08-11 03:27:19 0.32 earthquake
2019-08-11 03:29:20 4.3 earthquake
... ... ...
아웃라이어가 발생한 레코드를 삭제하기 전에 전체 데이터 분석 결과가 해당 아웃라이어로 인
해 달라지는 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.