Basic R

Basic-R

R Input/Output

Easy Input

# String 
"Hello World!"
print("Hello World!")
5+5

Output

[1] "Hello World!"
[1] 10

R Variables

  • To assign a value to a variable, use the <- sign. To output (or print) the variable value, just type the variable name:
  • 赋值操作用”<-“实现
  • 输出仅需要变量名即可
name <- "John"
age <- 40

name   # output "John"
age    # output 40
name <- "John"
age <- 40

name   # output "John"
age    # output 40
  • 多变量赋值
# Assign the same value to multiple variables in one line
var1 <- var2 <- var3 <- "Orange"

# Print variable values
var1
var2
var3

Output

[1] "Orange"
[1] "Orange"
[1] "Orange"

The Global Assignment Operator Normally, when you create a variable inside a function, that variable is local, and can only be used inside that function.

To create a global variable inside a function, you can use the global assignment operator «-

my_function <- function() {
txt <<- "fantastic"
  paste("R is", txt)
}
my_function()
print(txt)

Concatenate Elements

拼接结果

text1 <- "R is"
text2 <- "awesome"

paste(text1, text2)

Output

[1] "R is awesome"

R Data Types

  • numbers
    • numeric - (10.5, 55, 787) 小数
    • integer - (1L, 55L, 100L, where the letter “L” declares this as an integer) 整数
    • complex - (9 + 3i, where “i” is the imaginary part) 复数
  • character (a.k.a. string) - (“k”, “R is exciting”, “FALSE”, “11.5”) 字符串
  • logical (a.k.a. boolean) - (TRUE or FALSE) 布尔代数
# numeric
x <- 10.5
class(x)

# integer
x <- 1000L
class(x)

# complex
x <- 9i + 3
class(x)

# character/string
x <- "R is exciting"
class(x)

# logical/boolean
x <- TRUE
class(x)

Output

[1] "numeric"
[1] "integer"
[1] "complex"
[1] "character"
[1] "logical"

R Numbers

  • numeric
  • integer
  • complex

Type Conversion

任意两种类型之间的转换

as.numeric()
as.integer()
as.complex()

R math functions

Operator Name Example
+ 加法 x + y
- 减法 x - y
* 乘法 x * y
/ 除法 x / y
^ 指数 x ^ y
%% 取模(除法的余数) x %% y
%/% 整数除法(向下取整的除法结果) x %/% y

以上是常见的数学运算符及其含义。在表格中,第一列是运算符,第二列是对应的含义说明,第三列是示例演示了运算符的使用。

函数 用途
min() 找出一组数值中的最小值。
max() 找出一组数值中的最大值。
ceiling() 将数值向上取整。
floor() 将数值向下取整。
sqrt() 计算给定数值的平方根。
abs() 计算给定数值的绝对值。
round() 将数值四舍五入到最接近的整数。
sign() 确定给定数值的符号。返回-1、0或1,表示负数、零或正数。
sin() 计算给定角度的正弦值。
cos() 计算给定角度的余弦值。
tan() 计算给定角度的正切值。
asin() 计算给定值的反正弦值,返回一个角度值。
acos() 计算给定值的反余弦值,返回一个角度值。
atan() 计算给定值的反正切值,返回一个角度值。
exp() 计算给定数值的指数函数值。
log() 计算给定数值的自然对数。
log10() 计算给定数值的以10为底的对数。
log2() 计算给定数值的以2为底的对数。
log1p() 计算给定数值加1后的自然对数。
expm1() 计算给定数值的指数值减去1。

R Strings

str <- "Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua."

str # print the value of str

Output

[1] "Lorem ipsum dolor sit amet,\nconsectetur adipiscing elit,\nsed do eiusmod tempor incididunt\nut labore et dolore magna aliqua."

R will add a “\n” at the end of each line break. This is called an escape character, and the n character indicates a new line.

If you want the line breaks to be inserted at the same position as in the code, use the cat() function:

str <- "Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua."
cat(str)

Output

Lorem ipsum dolor sit amet,
consectetur adipiscing elit,
sed do eiusmod tempor incididunt
ut labore et dolore magna aliqua.
  • nchar() 返回字符串的长度
  • substr() 从字符串中提取子字符串
  • paste() 将多个字符串连接成一个字符串
  • paste0() 将多个字符串连接成一个字符串,但不添加空格
  • gsub() 用新的字符串替换字符串中的旧字符串
  • strsplit() 将字符串分割成多个子字符串
  • grepl() 检查该字符串是否在字符串

在字符串中间插入字符串

str <- "We are the so-called \"Vikings\", from the north."

str
cat(str)

# Output
[1] "We are the so-called \"Vikings\", from the north."
We are the so-called "Vikings", from the north.

用cat()合并

Code Result
\\ 反斜杠
\n 换行符
\r 回车符
\t 制表符
\b 退格符
\" 引号(双引号)

If-else

x <- 10
if (x > 5) {
  print("x is greater than 5")
} else if (x == 5) {
  print("x equals 5")
} else {
  print("x is less than 5")
}
  • AND: &
  • OR:

Loop

while

x <- 10
while (x > 5) {
  print(x)
  x <- x - 1
}

For

for (i in 1:10) {
  print(i)
}

# list

fruits <- list("apple", "banana", "cherry")

for (x in fruits) {
  print(x)
}

# vector

dice <- c(1, 2, 3, 4, 5, 6)

for (x in dice) {
  print(x)
}

Next: just like continue

fruits <- list("apple", "banana", "cherry")

for (x in fruits) {
  if (x == "banana") {
    next
  }
  print(x)
}
dice <- 1:6

for(x in dice) {
  if (x == 6) {
    print(paste("The dice number is", x, "Yahtzee!"))
  } else {
    print(paste("The dice number is", x, "Not Yahtzee"))
  }
}

Function

  • Creating a Function To create a function, use the function() keyword:
add <- function(x, y) {
  return(x + y)
}

add(10, 20)
  • Argument
my_function <- function(fname, lname) {
  paste(fname, lname)
}

my_function("Peter", "Griffin")

output

[1] "Peter Griffin"
  • Default Parameter Value
my_function <- function(country = "Norway") {
  paste("I am from", country)
}

my_function("Sweden")
my_function("India")
my_function() # will get the default value, which is Norway
my_function("USA")

output


[1] "I am from Sweden"
[1] "I am from India"
[1] "I am from Norway"
[1] "I am from USA"
  • Return values
my_function <- function(x) {
  return (5 * x)
}

print(my_function(3))
print(my_function(5))
print(my_function(9))

output

[1] 15
[1] 25
[1] 45
  • return multiple values
my_function <- function(x, y) {
  return(x + y, x - y)
}

Nested Function

Nested_function <- function(x, y) {
  a <- x + y
  return(a)
}

Nested_function(Nested_function(2,2), Nested_function(3,3))

output

[1] 10
Outer_func <- function(x) {
  Inner_func <- function(y) {
    a <- x + y
    return(a)
  }
  return (Inner_func)
}
output <- Outer_func(3) # To call the Outer_func
output(5)

Example Explained You cannot directly call the function because the Inner_func has been defined (nested) inside the Outer_func.

We need to call Outer_func first in order to call Inner_func as a second step.

We need to create a new variable called output and give it a value, which is 3 here.

We then print the output with the desired value of “y”, which in this case is 5.

The output is therefore 8 (3 + 5).

Recursion

tri_recursion <- function(k) {
  if (k > 0) {
    result <- k + tri_recursion(k - 1)
    print(result)
  } else {
    result = 0
    return(result)
  }
}
tri_recursion(6)

output

[1] 1
[1] 3
[1] 6
[1] 10
[1] 15
[1] 21

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