Dealing with vectors in R
Creating Vectors in R:
Vectors are the most basic R data objects and there are six types of atomic vectors. They are logical, integer, double, complex, character and raw.
Single element vector:
> x=’a’
> print(x)
[1] “a” # character type> x=1+2i
> print(x)
[1] 1+2i # complex type> x=11.26
> print(x)
[1] 11.26 # integer type> x=TRUE
> print(x)
[1] TRUE # logical typeMultiple element vector:
There are may ways to create vector in R. The commonly used techniques are:
- Using colon operator:
> v=2:10
> print(v)
[1] 2 3 4 5 6 7 8 9 10
> v=1.8:10.8
> print(v)
[1] 1.8 2.8 3.8 4.8 5.8 6.8 7.8 8.8 9.8 10.8
> v=1.5:10.1
> print(v)
[1] 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5
> v=1.8:10.5
> print(v)
[1] 1.8 2.8 3.8 4.8 5.8 6.8 7.8 8.8 9.8
2. Using seq() operator:
> print(seq(2, 10, by = 0.5)) #Create vector with elements from 2 to 10 incrementing by 0.5.
[1] 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
[17] 10.0
- 3. Using c() function:
> v=c(1,2,5,9,3)
> print(v)
[1] 1 2 5 9 3
If one of the elements in the vector is character, then the numeric and logical elements are converted into character type.
> v=c("white",5,8,TRUE)
> print(v)
[1] "white" "5" "8" "TRUE"
Accessing the elements of a vector:
> v=c(1,29,2,6,8,4)
To access the vector-elements we use the vector indexing method. Vector indexing can be done in 3 ways:
Using integer vector as index:
In R unlike most programming language the index starts from 1. [ ] are used for indexing. Giving negative integer values drops the corresponding value of the vector.
> v[1]
[1] 1
> v[c(1,3,6)]
[1] 1 2 4
> v[c(-1)]
[1] 29 2 6 8 4
Logical indexing:
> v[v>5] # filtering vectors based on conditions
[1] 29 6 8
> v[v<5]
[1] 2 4
III. Modifying a vector:
We can modify a vector using the assignment operator.
> v=c(1,29,2,6,8,4)
> v[3]=0 #Modifying 3rd element of the vector
> print(v)
[1] 1 29 0 6 8 4> v[v<5]=2 # Modifying elements less than 5 of the vector
> print(v)
[1] 2 29 2 6 8 2> v=v[1:4] #truncate first 4 elements of vector v
> print(v)
[1] 2 29 2 6Matrix:
I) Creating Vector Matrix in R:
> matrix(c(1:16),nrow=4,ncol=4)
[,1] [,2] [,3] [,4]
[1,] 1 5 9 13
[2,] 2 6 10 14
[3,] 3 7 11 15
[4,] 4 8 12 16
II) Eigenvalues and Eigenvectors:
> A=matrix(c(1,2,3,4,5,6,7,8,9),nrow=3)
> A
[,1] [,2] [,3] [1,] 1 4 7
[2,] 2 5 8 [3,] 3 6 9> det(A)==0
[1] TRUE> A=matrix(c(1,2,3,4,5,6,7,8,10),nrow=3)
> det(A)==0
[1] FALSE> E=eigen(A)
> names(E)
[1] “values” “vectors”> E$values
[1] 16.7074933 -0.9057402 0.1982469> E$vectors
[,1] [,2] [,3] [1,] -0.4524587 -0.9369032 0.1832951
[2,] -0.5545326 -0.1249770 -0.8624301 [3,] -0.6984087 0.3264860 0.4718233> det(E$vectors)
[1] -0.9593596
