R语言笔记（一）
文章目录
- 一、R objects
- 二、Types of data
- 三、Operators
- 1、Operators
- 2、Comparison operators
- 3、Logical operators
- 四、Check types of data objects
- 五、Convertion between data objects
- 六、R workspace
一、R objects
Two basic types of things/objects: data and functions
- Data: things like 6, “six”, 6.000 6.000 6.000, and [ 6 6 6 6 6 6 ] \left[ \begin{array}{ccc} 6 & 6 & 6 \\ 6 & 6 & 6\end{array}\right] [666666]
- Functions: things like
log,+(takes two arguments),<(two),sum(multiple), andmean(one)
二、Types of data
- Booleans
- Integers
- Characters
- Floating point numbers: an integer times a positive integer to the power of an integer, as in
3
×
1
0
6
3 \times 10^6
3×106 or
1
×
3
−
1
1 \times 3^{-1}
1×3−1
- Double precision: 64 bits (8 bytes); Single precision: 32 bits (4 bytes)
- Missing or ill-defined values:
NA,NaN, etc.
三、Operators
1、Operators
- Unary: take just one argument. E.g.,
-for arithmetic negation,!for Boolean negation - Binary: take two arguments. E.g.,
+,-,*, and/(though this is only a partial operator). Also,%%(for mod), and^(again partial)
- 一元运算符：只接受一个参数。例如，负号（-）用于算术取反，感叹号（!）用于布尔取反。
- 二元运算符：接受两个参数。例如，加号（+）、减号（-）、乘号（*）和除号（/）（尽管除号只是部分运算符）。还有求余运算符（%%），以及幂运算（^）（同样是部分运算符）。
# %/% 执行整除运算，即只保留商的整数部分，舍弃余数。
# %% 是取模运算符，它返回除法后的余数。
# %/% 和 %% 常配合使用来获取整数商和余数。
10 / 3 # 结果是 3.333333
10 %/% 3 # 结果是 3（商的整数部分）
10 %% 3 # 结果是 1（余数）
2、Comparison operators
These are also binary operators; they take two objects, and give back a Boolean.
6 > 5
6 < 5
6 >= 7
3、Logical operators
These basic ones are & (and) and | (or).
(5 > 7) & (6 * 7 == 42)
## [1] FALSE
(5 > 7) | (6 * 7 == 42)
## [1] TRUE
Note: The double forms && and || are different!
四、Check types of data objects
- The
typeof()function returns the data type is.x()functions return Boolean values indicating whether the argument is of type x
typeof(6)
## [1] "double"
is.double(7)
## [1] TRUE
## 解释：在 R 语言中，数字的默认类型是 双精度浮点数（double）。
is.na(7)
## [1] FALSE
is.na(7/0)
## [1] FALSE
## 解释：跟数学里不同，7/0 = Inf
is.na(0/0)
## [1] TRUE
五、Convertion between data objects
as.x()(tries to) “cast” its argument to type x, to translate it sensibly into such a value
as.character(5/6)
## [1] "0.833333333333333"
as.numeric(as.character(5/6))
## [1] 0.8333333
6 * as.numeric(as.character(5/6))
## [1] 5
5/6 == as.numeric(as.character(5/6))
## [1] FALSE
六、R workspace
Where do the variables live?
ls()
## [1] "approx.pi" "circumference" "diameter"
Getting rid of variables:
rm("circumference")
ls()
## [1] "approx.pi" "diameter"
rm(list=ls()) # Be warned! This erases everything
ls()
## character(0)