June 2020
Beginner to intermediate
522 pages
9h 6m
Chinese
Content preview from R 语言经典实例（原书第 2 版）
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第 15 章
简单编程
R 帮助你在不了解编程的情况下完成很多工作。编程打开了实现更多目标的大门，然而，
认真的 R 用户最终会进行某些程度的编程，从简单开始并且可能变得非常熟练。虽然这
不是编程手册，但本章列出了一些编程方法，R 用户通常认为这些编程方法对于开始他
们的编程之旅非常有用。
如果你已经熟悉编程和编程语言，这里的一些注释可以帮助你快速适应。（如果你不熟悉
这些术语，可以跳过这部分。）以下是需要注意到的一些 R 技术细节：
无类型变量
R 中的变量没有固定类型，例如整型或字符型，这与 C 和 Java 等类型语言不同。一
个变量可以在一个时刻是个数值，而下一刻变为数据框。
返回值
所有函数都返回一个值。通常，函数返回其函数体中最后一个表达式的值。你还可
以在函数内部的任何位置使用 return(
expr
) 。
按值调用参数
函数参数是“按值调用”
—
参数是严格的局部变量，对这些变量的更改不会影响
全局变量的取值。
局部变量
只需为其一个变量赋值即可创建局部变量。显式的对变量进行声明不是必需的。当
函数退出时，局部变量将丢失。
全局变量
全局变量保存在用户的工作空间中。在函数中，你可以使用赋值运算符 <<- 更改全
局变量，但不鼓励这样做。
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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.