R - Hello World (Data Types and Vector)

• Start : Install R and R Studio 

• Five basic Classes of Objects(data types) in R

• character
• numeric (if you give 1 for variable, it will give numeric Object)
• integer (you could give variable x with 1L for giving integer Object)
• complex
• logical (Ture or False)

• Inf and NaN
• Inf means infinite, for example, 1/0 will give you Inf
• NaN means Not a Number, for example, 0/0 will give you NaN
• Comment
• # indicates comment

  x <- 100 # this is comment  

• "Hello World"
• Give variable x "Hello World" and print it to the console

 > x <- "Hello World"  # <- symbol is the assignment operator
 > print(x)  
 [1] "Hello World"  

• Vector : A basic Object contains the same Classes of Objects
• In "Hello World" example, x is a Vector and the first element is "Hello World"
• Create Vector using c() function & vector() function

 > x <- c(0.5, 0.6)  
 > x  # print x
 [1] 0.5 0.6  
 > x <- vector("numeric", length = 10)  
 > x  # print x
  [1] 0 0 0 0 0 0 0 0 0 0  

• What if we create vector with different Objects? A: Coercion will occur

 > y <- c(1.7, "a")  
 > y  # 1.7 will be changed to character "1.7"
 [1] "1.7" "a"   

• Connect string with paste() function

 > a <- c("Blog","address","is")  
 > a  
 [1] "Blog"  "address" "is"     
 > paste(a,collapse=" ")  
 [1] "Blog address is"  
 > b <- c(a,"parklize.blogspot.com")  
 > b  
 [1] "Blog"         "address"        "is"            
 [4] "parklize.blogspot.com"  
 > paste(b,collapse=" ")  
 [1] "Blog address is parklize.blogspot.com"  
 > c <- paste("Blog","address","is","parklize.blogspot.com",sep=" ")  
 > c  
 [1] "Blog address is parklize.blogspot.com"  

• Check vectors are identical or not..

 > x <- c(1:5)  
 > y <- 1:5  
 > identical(x,y)  
 [1] TRUE  
 > names(x) <- c("a","b","c","d","e")  
 > identical(x,y)  
 [1] FALSE  

• Explicit Coercion
• Object could be coerced from one class to another class with as.* function

 > y <- 1.7  
 > class(y)  
 [1] "numeric"  
 > y <- as.character(y)  # explicitly coerce to character Object
 > class(y)  
 [1] "character"  

• Get help for function
• str("function name") will get brief information and ?"function name" to get more details

 > str(matrix)  # check matrix() function in brief
 function (data = NA, nrow = 1, ncol = 1, byrow = FALSE, dimnames = NULL)   
 > ?matrix  # get help page on the matrix() function

• Get help for operator
• If you want to know what the operator ":" does...use ?':' and it will open the help page.

 > ?':'  
 starting httpd help server ... done  

• List variables in your workspace

 > x <- 1:4  
 > ls()  
 [1] "x"  

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