August 2022
Beginner to intermediate
463 pages
9h 22m
Chinese
Content preview from Tableau Prep即学即用
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106
｜
第
12
章
12.4
采样技术
默认情况下，每当你连接数据集时，
Prep Builder
都会使用样本数据（见图
12-1
）。
图
12
-
1
：Tableau 的默认输入采样
通过巧妙地使用算法，
Prep Builder
可以自动显示你的数据、类别和数值分布的完整
形态，而不必操作运行完整的数据集的各个步骤，直至你准备好生成最终的输出。
此时，
Tableau
将使用完整的输入数据集，除非另有指示。如果你的数据集体量较小，
Tableau
将使用完整的数据集，但如果你的数据集较宽（列数较多），
Tableau
的默
认采样将比你的数据集窄些（列数较少），即此时会返回较少的数据行和记录。
即使
Prep Builder
正在对数据进行采样，你可能也想自己控制采样。在输入步骤中，
有两个基本控制手段。
12.4.1
固定行数
固定的行数将取自数据源中开头的那些行。这些行不一定是按照什么特定的顺序，
因为数据集根据它们加载和存储数据的方式来保存数据。图
12-2
展示了可以设置要
返回的行数的界面。
｜
107
数据集采样
图
12
-
2
：Fixed number of rows（固定行数）选项
12.4.2
随机采样
你可以通过将
Sampling method
（采样方法）方法选项改为
Random sample
（随机采
样）来进一步控制样本提取（见图 ...
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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.