Basic syntax and common commands of R language

R In fact, it is just a tool for data analysis , So at the beginning, you don't need to learn how deep and how detailed , You just need to be able to meet your current needs , Later, learn slowly in practice .
After all, I want to R It is not easy to learn . The correct way is to learn while doing , It won't be google Turn over the document .
This film is mainly about R Basic syntax and common command operations

assignment

R Assignment adoption <- perhaps -> perhaps =, The first of the standards is recommended .
because R A function with the same name is built in c(), It is best not to use... In coding c As object name , Otherwise, some imperceptible problems may arise

a <- 133
"hello" -> b  #  Pay attention to either way , The greater than or less than sign points to the variable name 
d = 'This'  #  This is not recommended , It may cause problems 

a
b
d

133

'hello'

'This'

view help

help(mean)
#  perhaps 
?mean

Package installation and loading

#  Get contains R Package library location 
.libPaths()

#  View the packages that have been installed 
library()

#  Installation package 
install.packages("packagename")

#  Load package 
library(packagesname)

#  View the loaded packages 
(.packages())

#  Unload the loaded package （ Note that it is not to delete the package ）
detach("package:packagename")

#  Delete package 
remove.packages("packagename")

Data reading and saving

Read

#  Read csv
data <- read.csv('.\\ statistical \\example\\ch1\\table1_1.csv') 
head(data,6)    #  Before reading  6 Row data 

#  Read  Excel data 
library(xlsx)    # Need to install  xlsx  package 
data <- read.xlsx("file",n)    # n  Is the sequence number of the worksheet to import 

#  Read  spss data 
library(foregin) #  Installed by default 
data <- read.spss("file",use.value.labels=TRUE,as.data.frame=TRUE)

#  Read  R Format data 
data <- load('.\\ statistical \\example\\ch1\\example1_1.RData')

The student's name	statistical	mathematics	Marketing	Management	Accounting
Zhangqingsong	68	85	84	89	86
Wang Yuxiang	85	91	63	76	66
Tian Siyu	74	74	61	80	69
Xulina	88	100	49	71	66
Zhang Zhijie	63	82	89	78	80
Zhaoyingying	78	84	51	60	60

preservation

#  preservation  R Format data 
save(data,file = '.\\...\\name.Rdata')

#  preservation  csv Format data 
write.csv(data,file = '.\\...\\name.csv')

#  preservation  xlsx Format 
library(xlsx)
write.xlsx(data, "data.xlsx",sheet.name="sheet1")

if Conditional statements

if sentence

x <- 30L  # R In language , Add... To a positive integer  L To represent integer data （ Positive integer ）
if(is.integer(x)) {
   print("X is an Integer")
}

[1] "X is an Integer"

if…else sentence

y <- list('a', 'v', 'd')
if('a' %in% y){    # %in%  Operator   Check whether the element is in the vector 
    print('a is in list')
}else{      #  Notice the  else The statement is not in if In the curly brackets of 
    print('a is not in list')

}

[1] "a is in list"

x <- c("what","is","truth")

if("Truth" %in% x) {
   print("Truth is found the first time")
} else if ("truth" %in% x) {
   print("truth is found the second time")
} else {
   print("No truth found")
}

[1] "truth is found the second time"

switch sentence

#  Create a function , The input value and the selected function type to output the result .
centre <- function(x, type) {

switch(type,

       mean = mean(x),

       median = median(x),

       trimmed = mean(x, trim = .1))

 }
centre(c(1,2,4,5),'mean')

3

Loop statement

while loop

ant <- 2
while(ant<5){
    print('hello')
    ant = ant + 1
}

[1] "hello"
[1] "hello"
[1] "hello"

for loop

v <- LETTERS[1:4]  # LETTERS by 26 A vector of capital letters .

for(i in v){
    print(i)
}

[1] "A"
[1] "B"
[1] "C"
[1] "D"

repeat loop

i <- 1
sum <- 0
repeat
{
   sum = sum + i
   if( i >= 100)   # If it has been added circularly to 100, Then use break Jump out of repeat loop 
       break
   i <- i + 1
}
print(sum)

[1] 5050

next sentence

R Language exists next sentence , We can use when we want to skip the current iteration of the loop without terminating it next. encounter next when ,R The parser skips this iteration , And start the next iteration of the loop .

k <- LETTERS[1:6]
for ( i in k) {
   if (i == "D") {
      next
   }
   print(i)
}

[1] "A"
[1] "B"
[1] "C"
[1] "E"
[1] "F"

R Common constants

# 26 Capital letters 
LETTERS

# 26 Lowercase letters 
letters

#  Abbreviate the month 
month.abb

#  The name of the month 
month.name

# π  value 
pi

'A' 'B' 'C' 'D' 'E' 'F' 'G' 'H' 'I' 'J' 'K' 'L' 'M' 'N' 'O' 'P' 'Q' 'R' 'S' 'T' 'U' 'V' 'W' 'X' 'Y' 'Z'
'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j' 'k' 'l' 'm' 'n' 'o' 'p' 'q' 'r' 's' 't' 'u' 'v' 'w' 'x' 'y' 'z'
'Jan' 'Feb' 'Mar' 'Apr' 'May' 'Jun' 'Jul' 'Aug' 'Sep' 'Oct' 'Nov' 'Dec'
'January' 'February' 'March' 'April' 'May' 'June' 'July' 'August' 'September' 'October' 'November' 'December'
3.14159265358979