R Object
R Vector
vec1= c(2,3,4,5)
vec1
## [1] 2 3 4 5
# Subsetting the first element in vec1
vec1[1:3]
## [1] 2 3 4
# Character vectors
vec2 = c("Male", "Female")
vec2
## [1] "Male" "Female"
# Creating sequence number vectors
vec3 = seq(1, 10, 1)
vec3
## [1] 1 2 3 4 5 6 7 8 9 10
vec3 = 1:10
vec3
## [1] 1 2 3 4 5 6 7 8 9 10
vec3 = seq(1, 10, 2)
vec3
## [1] 1 3 5 7 9
vec3 = seq(1, 10, length.out=5)
vec3
## [1] 1.00 3.25 5.50 7.75 10.00
R Matrices/Array
mat1 = matrix(c(3,2,1,4), nrow = 2, byrow = TRUE)
mat1
## [,1] [,2]
## [1,] 3 2
## [2,] 1 4
dim(mat1)
## [1] 2 2
# Subsetting in a matrix
mat1[1,1]; mat1[1,2]; mat1[1, ]; mat1[ ,1]
## [1] 3
## [1] 2
## [1] 3 2
## [1] 3 1
det(mat1) # Determinant`
## [1] 10
solve(mat1) # Inverse
## [,1] [,2]
## [1,] 0.4 -0.2
## [2,] -0.1 0.3
mat2 = solve(mat1)
mat1 + mat2 # Addition
## [,1] [,2]
## [1,] 3.4 1.8
## [2,] 0.9 4.3
mat1 %*% mat2 # Multiplication
## [,1] [,2]
## [1,] 1 0
## [2,] 0 1
mat1 - mat2 # Subtraction
## [,1] [,2]
## [1,] 2.6 2.2
## [2,] 1.1 3.7
eigen(mat1)
## eigen() decomposition
## $values
## [1] 5 2
##
## $vectors
## [,1] [,2]
## [1,] -0.7071068 -0.8944272
## [2,] -0.7071068 0.4472136
Array
arr = array(list(mat1, mat2))
arr
## [[1]]
## [,1] [,2]
## [1,] 3 2
## [2,] 1 4
##
## [[2]]
## [,1] [,2]
## [1,] 0.4 -0.2
## [2,] -0.1 0.3
arr = array(c(mat1, mat2), dim=c(2,2,2))
arr
## , , 1
##
## [,1] [,2]
## [1,] 3 2
## [2,] 1 4
##
## , , 2
##
## [,1] [,2]
## [1,] 0.4 -0.2
## [2,] -0.1 0.3
arr[,,1]; arr[,,2]; arr[1,,]; arr[2,,]; arr[1,1,1] # arr[row, column, Matrix]
## [,1] [,2]
## [1,] 3 2
## [2,] 1 4
## [,1] [,2]
## [1,] 0.4 -0.2
## [2,] -0.1 0.3
## [,1] [,2]
## [1,] 3 0.4
## [2,] 2 -0.2
## [,1] [,2]
## [1,] 1 -0.1
## [2,] 4 0.3
## [1] 3
List
list1 = list(vec1, vec2, vec3, mat1, mat2)
print("The elements of list1 are")
## [1] "The elements of list1 are"
# Subletting list1
list1[1] # returns vec1
## [[1]]
## [1] 2 3 4 5
list1[[1]][2] # returns the second element of vec1 in list1
## [1] 3