August 2018
Intermediate to advanced
227 pages
4h 16m
Chinese
Content preview from 高效R语言编程
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94
第
5
章
高效输入
/
输出
本章介绍
R
中如何高效读
/
写数据。
Input/Output
（
I/O
）是 读
/
写数据的技术术语：
将信息加载进特定的计算机系统（此时指
R
），然后再将其输出到外部世界（指
输出为其他软件可读的文件格式）。在数据来自外部资源或许要输出数据到
外部资源的项目中，数据
I/O
过程将是必须的。但主要的
R
资源与文档均假
设了你的数据已经被加载进你的项目中，而忽视将数据集导入
R
中与输出数
据到
R
以外的环境是个耗时的、棘手的过程的事实。复杂的、进展缓慢或者
最终未成功的数据
I/O
过程在项目的一开始就降低项目的效率。相反，高效
读写你的数据将使你的项目在外部世界更容易成功。
第一节介绍
rio
,
可以高效读
/
写多种格式文件数据的元包。
rio
只需要两个直
观的函数即可完成数据的
I/O
操作，所以学习和应用起来非常高效。接着，
我们详细探讨了
readr
与
data.table
包中的高效读入普通纯文本文件的函数。
最后介绍了二进制格式，二进制文件格式可大幅缩小文件大少以及读写时间。
随着数字革命的加速以及开源数据的增长，世界上越来越多的数据可从网上
下载。这种趋势仍在继续，下载以及导入网络数据是适应未来的
I/O
技能
,
在
本章后面的“从以太网获取数据”一节中介绍了这部分内容。本章的基准测
试说明了选用合适的文件格式和处理数据的
I/O
包会对计算效率产生巨大影
响。
在读取一行数据之前，应该先考虑一下可重复数据管理的通用规则
:
不要改写
原始数据文件。原始文件应被视为只读的，并包含数据来源的信息。即使数
据不对外公开
,
保留原始文件名字并说明它的来源， ...
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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.