R Language: basic data types and the operation symbol R (a)

Into R:

1. variable assignment

• "->" and "=" There are subtle differences, their role in the program range in scope after the assignment is different;
• In order to maintain a consistent programming divisions, we recommended to use the "<-" symbol at the time of the assignment;

2.R script

R script concept is simple, it is a document code there, is **. R ** is the end. When using R to do the analysis, we sometimes write long code, and the code that we want after repeated changes can be used, then we need to use the R script to store our code.

3. Create the script R:

In order to open the Rstudio: "File - New - File - R Script"

4.R code runs

** Note: ** Code in R need to select the code you want to run click "run" to run the upper right corner, you can use shortcut keys "ctrl + enter" to run.

---

Five basic data types:

Basic concepts and operations

Variables: variable is derived from a mathematical abstraction, can be stored in a computer language calculation result or "means that a particular value"

VS constant variable: specific things in motion, if a certain amount remains the same, it is called constant; on the contrary, it is called variable

Data type: a set of properties and the set value of the same general term for a set of operations defined in this set of values;

Store different data types of variables: the data type of the variable group, the programming language of the data type matches the assigned memory space for storage.

Data corresponding to R five basic types:

• Character - Character
• Numeric - Digital
• Integer - integer
• Complex * - plural
• Logical - Logical number

# 变量
# 变量储存计算结果
result <- 1+2*3/4
result

# 变量表示值的抽象概念
company <- "公司A"
company
company <- "公司B"
company

# 赋值运算符
n <- 10 #将数值10赋值给变量n
10 -> n #箭头也可以向右
n = 10 #除了箭头外，等号也可以用来赋值

_______________________________________________________________________________________________________________

# 五种基本数据类型
ch <- "你好" 
n <- 1.23
i <- as.integer(1)
co <- 1+2i
lo <- TRUE

Common data types: Date and Time

Date - Date:

• Mutator: as.Date ()

Time - TIme

• POSIXct class represents: the internal storage of a large integer - assignment function as.POSIXct
• POSIXlt: internal storage is a list containing all kinds of time information (year, month, day, time ......) - mutator as.POSIXlt
  • unclass () function will open this list
  • $ + List for a specific element name: Display specific element values

# 日期（Date）和时间（Time）
# 定义日期变量
x1 <- as.Date("2015-03-26")
x2 <- as.Date("2015-01-02")
x1
x2


# 日期变量的专属操作
x1-3 ## 日期减去整数
x1 - x2 ## 两个日期的差值
class(x1-x2) ## 产生difftime的数据类型，表示两个日志相差的天数
as.integer(x1 - x2) ## 将 difftime直接转换成整数


## 定义一个 POSIXct 类型的时间变量
tm1 <- as.POSIXct("2013-07-24 23:55:26") 
tm1
as.integer(tm1) ## 查看tm1所对应的整数
tm1-3 ## POSIXct减去3


## 定义一个 POSIXlt 类型的时间变量
tm2 <- as.POSIXlt("2013-07-24 23:55:26")
tm2

# class(tm2) ## 显示tm2的类别 - POSIXlt
unclass(tm2) ## 返回POSIXlt值背后，定义它的列表
tm2$sec ## $+名称，显示POSIXlt列表名称对应的数值

R Operator:

Data analysis of the most common types of operators.