The matrix is an important data type in R language similar to the data frame. It has two dimensions as the arrangement of elements is in rows and columns.
Question: What is a matrix in R Language?
Answer: In R language matrices are two-dimensional arrays of elements all of which are of the same type, for example, numbers, character strings, or logical values.
Matrices may be constructed using the built-in function “matrix”, which reshapes its first argument into a matrix having a specified number of rows as the second argument and a number of columns as the third matrix.
Question: Give an example of how the matrix is constructed in R language.
Answer: A 3 by 3 matrix (3 rows and 3 columns) matrix may be constructed such as:
matrix(1:9, 3, 3) matrix(c(1,2,3,4,5,6,7,8,9), 3, 3)matrix(runif(9), 3,3)
First, two commands construct a matrix of 9 elements having 3 rows and 3 columns consisting of numbers from 1 up to 9. The third command makes a matrix of 3 rows and 3 columns with random numbers from a uniform distribution.
Question: How the matrix elements are filled?
Answer: A matrix is filled by columns, unless the optional argument byrow is set to TRUE as an argument in matrix command, for example
matrix(1:9, 3, 3, byrow=TRUE)
Question: Can the matrix be stored in R?
Answer: Any matrix can be stored in R such as
m <- matrix(1:9, 3, 3) mymatrix <- matrix( rnorm(16), nrow=4 )
Matrices are stored in “m” and “mymatrix” objects. The second command constructs a matrix having 16 elements with 4 rows from a normal distribution having mean 0 and variance 1.
Attributes of Matrix object in R
Question: what is the use of the dim command in R?
Answer: The dim (dimension) is an attribute of the matrix in R, which tells the number of rows and the number of columns of a matrix, for example,
dim(mymatrix)
This will result in output showing 4Â 4, meaning 4 rows and 4 column matrix.
Question: Can we name rows of a matrix in R?
Answer: Yes in R language we can name rows of a matrix according to one’s requirements, such as
rownames(mymatrix) <- c("x1", "x2", "x3", "x4")
mymatrixQuestion: Can column names be changed or updated in R?
Answer: The procedure is the same as changing the column name. For this purpose colnames command is used, for example
colnames(mymatrix)<-c("A", "B", "C", "D")
mymatrixQuestion: What is the purpose of the attributes command for the matrix in R?
Answer: The attributes function can be used to get information about the dimension of the matrix and dimnames (dimension names). For example;
attributes(mymatrix)