September 2013
Intermediate to advanced
264 pages
5h
Chinese
Content preview from Bad Data 技術手冊
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壞的現實
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127
不幸的是，除了分割之外，還有許多的狀況是需要調整股息的，而有些則是不用的。所
以追蹤多個時間序列資料是很重要的，有時甚至三個都要：價格、分割調整以及股息
調整。
壞的現實
有時，「顯然的」壞資料是正確的。看起來奇怪的資料也許反映了壞的現實，不論是因
為技術性的錯誤還是不理性的人類。
一個著名的「準確的」壞資料範例，就是聯合航空（當時的股票編號是 UAUA，現在則
為 UAL）股價崩盤事件，當時是因為 Google News 的爬蟲重新發佈了一篇有六年歷史
之久的聯合航空宣佈破產的消息。
在 2008 年 9 月 6 日，Google News 的爬蟲拜訪了在
South Florida Sun Sentinel
中， 聯
合航空在 2002 年時的破產消息的庫存故事。該故事的內文中並沒有包含日期，所以
Google News 預設的將它標為當前的日期。在 9 月 8 日時，有個獨立的投資顧問看到了
該故事，並且認為它是目前正在發生的事情，然後將它發佈到一個供人訂閱的財務新聞
頻道中。交易員們看到該頭條，都盡快的想要將 UAUA 賣出，而沒有將該故事看完。
UAUA 隨即在五分鐘之內從一股 $12 跌到一股 $3。幾分鐘之後，UAUA 的交易暫停了
一小時，讓大家喘口氣並且想想發生了什麼事情。在這之後，交易好像沒有發生過任何
事般的恢復了。
許多的資料清除演算法會將這種在短時間內明顯的錯誤價格資料移除。然而，這個價
格的確有發生；而真實的金錢也被交換了。在十分鐘之內，15% 的 UAUA 股票以及 ...
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