August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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｜
347
处理兑换率
38.2
在
Tableau Prep
中应用兑换率
利用
Preppin
’
Data
：第
6
周挑战赛（
https://oreil.ly/dMwG3
）的数据集，让我们完成
从英镑（
GBP
）到美元（
USD
）的货币转换。
38.2.1
第
1
步：为转换创建一致的数据粒度
首先，你需要导入输入数据（见图
38-1
和图
38-2
）。
图
38
-
1
：兑换率数据集
图
38
-
2
：Sales（销售额）数据集
这两个数据集最初还没有准备好进行转换，因为你还没有一个字段用来连接它们。
对于这些数据集，需要将各个日期从按照天的方式“卷起”到按照星期的方式“卷起”，
以匹配图
38-1
中兑换率表中的
Date
列。这是数据识别的要求。最终，你需要决定
用什么频率来进行数据转换，然后找到该时间段内的兑换率，并确保该时间段级别
内的兑换率保持正确。
348
｜
第
38
章
这个例子需要你找到最好和最坏的转换方案。换句话说，数据准备任务是找到每周
1
英镑所能兑换的美元的最小值和最大值。其他需要考虑的情况包括：
•
寻找一个时段内的平均值。
•
寻找“起始”或“结束”值，作为可能是该时间段内兑换价值的指标。
提出问题的背景，决定着最终你需要采用哪种技术。
38.2.2
第
2
步：将数据集连接在一起
使用
Prep Builder
中的连接步骤，现在可以将两个不同的数据集连接在一起（见图 ...
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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.
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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.