R语言基本语法

更新一下r语言语法，因为课上要用到。

1.1 变量名命名规则：

  R 语言的有效的变量名称由字母，数字以及点号 . 或下划线 _ 组成。

  变量名称以字母或点开头。

 

 1.2 变量赋值与处理：

# three naming methods
var.1 = c(1,2,3,4)
print(var.1)
var.2 <- c("hello")
print(var.2)
c("hello") -> var.3
print(var.3)

#show the defined variations and delete 'x' and 'y'
print(ls())
rm(x)
rm(y)
print(ls())

注：

 

 

1.3 输入输出：

#input and output
print("hello world")
cat(1,"add",1,"=",2)
#just as in python
#cat() 函数支持直接输出结果到文件：
cat("text.....", file="C:/Users/xxx/Desktop/R语言工程/learn R/text.txt")
#sink() 函数可以把控制台输出的文字直接输出到文件中去：
#这条语句执行以后，任何控制台上的输出都会被写入到文件中去，控制台将不会显示输出。
#注意：这个操作也是"覆盖写入"操作，会直接清除原有的文件内容。
#如果我们依然像保留控制台的输出，可以设置 split 属性：
sink("C:/Users/xxx/Desktop/R语言工程/learn R/test.txt", split=TRUE)
print("test..test...")
#如果想取消输出到文件，可以调用无参数的 sink ：
sink()
#从文件读入文字
readLines("C:/Users/xxx/Desktop/R语言工程/learn R/test.txt")
#关于工作目录的获取：
print(getwd())
# 设置当前工作目录
setwd("xxx")
# 查看当前工作目录
print(getwd())

 1.4 注释：

if(FALSE) {
    "
    这是一个多行注释的实例
    注释内容放在单引号或双引号之间
    "
}

1.5 数学计算相关函数：

# calculation
#赋值
a <- 123
b <- 456
print(a+b)
#当然，= 也可以使用

#乘方运算
c = 2^3
print(c)

#整除求余数
d = 7%%3
print(d)

#整除
d = 7%/%3
print(d)

#向右赋值
8 -> e
print(e)

#创建一系列数字的向量
v <- 1:10
print(v)

#判断数字是否在向量v中：
v1 <- 3
v2 <- 15
print(v1 %in% v)
print(v2 %in% v)

#一些基本数学函数：
f = sqrt(20)
print(f)
i = exp(10)
print(i)
j = log (2,8)
print(j)
k = log10(10)
print(k)

#取整函数：
print(round(2.56676767))
print(round(2.56676767,4))
print(ceiling(2.5656))
print(floor(2.5656))

#关于三角函数(弧度制表示)
print(sin(pi/6))
print(asin(0.5))

#关于概率中的正态分布：
print(dnorm(0)) #概率密度函数
print(pnorm(0)) #分布函数值
print(qnorm(0.95))#分位数函数
print(rnorm(3,5,2))#概率仿真，产生三个均值为5，标准差为2的数字

 1.6 数据类型：

 

 

###vector###
a = c(1,2,3,4,5)
print(a[1])
#three methods of extracting elements from vector
print(a[2:4])
print(a[c(1,3,5)])
print(a[c(-1,-5)])
#alterations:
print(sort(a))
print(rev(a))
print(order(a))
print(a[order(a)])
#vector generations
print(seq(1,9,2))
print(seq(0,1,length.out = 3))
print(rep(0,6))
#about NA and NULL:NULL is actually nothing
print(length(c(NA,NA,NULL,NULL)))
a = c(NA,NA,NULL)
print(a)
#Logical vector
a = c(11,12,13)
b = a > 12
print(b)
  #function which() filtrates TRUE in vector
  #an example:
which(b)
vector_test =c(1,2,3,4,5,6,7,8,9,10)
print(vector_test[which(vector_test>=5 & vector_test<=9)])
#strings:
print(toupper("This is an example"))
print(tolower("This is an example"))
print(nchar("This is an example",type="bytes"))
print(nchar("This is an example",type="char"))
#print(substr("This is an example"),1,10)
#print(substring("This is an example"),6)
print(as.numeric("123"))
print(as.character(12.34))
print(strsplit("2022;7;19",";"))
print(gsub("/", "-", "2022/7/19"))

 

###matrix###
#creation of matrix:
#default: cols
vector = c(1,2,3,4,5,6,7,8,9)
matrix_1=matrix(vector,3,3)
print(matrix_1)
#rows
print(matrix_1[2,3])
#add names:
colnames(matrix_1)=c('a','b','c')
rownames(matrix_1)=c('e','f','g')
print(matrix_1)
matrix_2= matrix(vector,3,3,byrow=TRUE)
print(matrix_2)
#matrix calculations
m1 = matrix(c(1,2),1,2)
m2 = matrix(c(3,4),2,1)
print(m1 %*% m2)
#get inverse matrix
a = matrix(c(1,3,2,4),2,2)
print(a)
print(solve(a))
#calculate the cols and rows
print(apply(a,1,sum))
print(apply(a,2,sum))

 

###list###
#creation:
list_001 <- list("good",123,c(1,2,3),"bad",12.32)
print(list_001)
names(list_001)<-c("string","number","vector","string","float")
print(list_001)
#visit the lists:
print(list_001[3])
print(list_001[4])
print(list_001$number)#use the names to find elements
#add:
list001<-"new elements"
#delete
list_001[2]<-NULL
#merge the lists:
list_002 <- list("list002_1","list002_2","list002_3")
list_003 <- c(list_001,list_002)
print(list_003)
#turn the lists into vetctor:
v1 <- unlist(list_001)
v2 <- unlist(list_002)
print(v1)
print(v2)

 

 1.7 判断语句和循环语句：

#if ... else
#switch
a <- 4
x <- switch(
  a,
  "a",
  "b",
  "c",
  "d",
  "e"
)
print(x)
#if no in range ,return NULL

#three ways: repeat,while,for 
#001 repeat:never get out until TRUE or break
n <- 1
repeat{
  print(1)
  n <- n+1
  if(n>5){
    break
  }
}
#002 while
while(i<7)
{
  print(2)
  i <- i+1
}
#003 for 
v <- LETTERS[1:4]
for(i in v)
{
  print(3)
}
#and the control sentence: next and break

 1.8 函数

#creation:
i <- 0
function001 <- function(data1,data2)
{
repeat{
  i <- i+1
  print("test...")
  if(i>=(data1+data2))
  {
    break
  }
}   
for (i in 1:data1)
{
  print("ha")
}  
}

function001(3,1)
#R is lazy and the following is'nt error
newfunction <- function(x1)
{
  200
}
print(newfunction(20))

 1.9 关于数据框:

 

#create a table
table = data.frame(
  name = c ("Mr.K","Mr.M","Mr.G"),
  salary = c(30000,45000,60000),
  work = c("001","002","003")
)
print(table)

#show the data structure of table:
print(str(table))
#show the further analysis of the table:
print(summary(table))
#get the cols of the table:
result <- data.frame(table$name,table$salary)
print(result)
#print the former two rows:
result <- table[1:2,]
print(result)
#add information
table2 = data.frame(
  name = c("skeleton","steve","creeper"),
  damage = c(10,10,100)
)
table2$cost<-c("20","25","50")
print(table2)
#stick all the vectors into a new table:
name <- c("farmer","strong farmer","hunter")
costs <- c(10,15,25)
heart <- c(20,35,15)
damage <- c(5,5,20)
table3 <- cbind(name,costs,heart,damage)
print(table3)