- assignment statements (賦值): create new objects with
<-.Don’t be lazy and use=: it will work, but it will cause confusion later. 在RStuido中快速鍵：Alt+-(the minus sign)
# create new objects with <-
object_name <- value
4.2 What’s in a name? 命名習慣與規則
- Object names must start with a letter, and can only contain letters, numbers,
_and. - 命名最好帶有意義，以便日後重讀code時容易讀懂
- 作者推薦以 snake_case命名：以底線_分隔小寫字母
i_use_snake_case
otherPeopleUseCamelCase
some.people.use.periods
And_aFew.People_RENOUNCEconvention
- 輸入文字按 Tab 鍵，會列出符合輸入文字的物件、函數、功能……，等所有指令
- 按F1鍵，會跳出相關的help檔
- The
+tells you that R is waiting for more input. Usually that means you’ve forgotten either a"or a).
4.3 Calling functions
# y <- seq(1, 10, length.out = 5)
# y
#This common action can be shortened by surrounding the assignment with parentheses,
#which causes assignment and “print to screen” to happen.
(y <- seq(1, 10, length.out = 5))
- 在RStudio右上方的Environment可以查看我們所建立的所有的object
Exercise 4.1
容易造成bug，不易分辨的兩組英文字母及數字：
- the numeral zero (0), the Latin small letter O (o), and the Latin capital letter O (O),
- the numeral one (1), the Latin small letter I (i), the Latin capital letter I (I), and Latin small letter L (l).
Error messages of the form "object '...' not found" mean exactly what they say. The most common scenarios in which I encounter this error message are
- I forgot to create the object, or an error prevented the object from being created.
- I made a typo in the object’s name, either when using it or when I created it (as in the example above), or I forgot what I had originally named it. If you find yourself often writing the wrong name for an object, it is a good indication that the original name was not a good one.
- I forgot to load the package that contains the object using
library().
Exercise 4.3
Press Alt + Shift + K, this gives a menu with keyboard shortcuts. This can be found in the menu under Tools -> Keyboard Shortcuts Help.
Megan's Note 