September 2013
Intermediate to advanced
264 pages
5h
Chinese
Content preview from Bad Data 技術手冊
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第二章：是只有我這樣，還是這個資料本身令人感到有趣？
驗證欄位
當你能夠讓資料變成可以被檢視並且被操作的格式時，下一步就是要去理解資料代表的
意義。在某些（極為少數的）狀況中，所有關於資料的資訊都會被提供。但通常都不會
這麼幸運，而需要花上一些時間來理解資料。依照資料格式的不同，也許會有一些標頭
列能夠提供一些線索，或是每個資料元素可能會擁有對應的鍵。若你很幸運，它們將會
用你能夠理解的語言以適當的文字敘述，或者至少能讓你找到某人來閱讀該敘述。我就
曾經不止一次的尋求一個俄國 QA 人員的幫助。這也是工作環境多元化的好處之一。
一個常見的錯誤就是誤解了內容的單位或是欄位的意義。像貨幣欄位就可以用元、角、
分等單位描述。收益的欄位也可以是總收益或是淨收益。距離可能是使用英哩、公里、
英尺等等為單位。去看定義以及實際在欄位中的值，都能夠幫助我們盡量不要因為誤解
而導致不正確的結論。
你也應該要看其他欄位的值，確保所有的欄位看起來都很合理。舉例來說，頁面瀏覽次
數的欄位內容應該是一個整數，而不會有小數點的數字或是字串。貨幣欄位（價格、成
本、PPC 或 RPM）應該就是包含兩位或是四位小數點的數字。使用者名稱欄位應該要
包含看起來像是一般使用者名稱的字串。IP 位址則是被句點隔成四部分的整數。
在資料集合中的常見問題就是遺失值或是空值。有時候這樣並沒有關係，但有時候會
造成記錄的錯誤。這種值會用許多不同的方式表達，有時候就什麼都沒有（如在以 tab
分隔的檔案中的兩個連續 tab）、空字串（包含單引號或是雙引號）或是寫著 ...
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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.