A matrix is simply a set of numbers arranged in rows and columns to form a rectangular array. The numbers inside a matrix are called the elements, or entries, of the matrix.
In this shot, we want to look at matrices in
R and access the elements present in a matrix. Before learning how to access the elements of a matrix, let’s see how a matrix can be created using the
matrix() function in
R is simply used to create a matrix.
The syntax of the
matrix() function is given as:
matrix(data, nrow, ncol, byrow, dimnames)
The parameter values of the
matrix() function take the following parameters:
data: This is a required value. It is the input vector which becomes the data elements of the matrix.
nrow: This is a required value. It is the desired number of rows.
ncol: This is a required value. It is the desired number of columns.
byrow: This is an optional value. It is logical. If
FALSEby default, the matrix is filled by columns. If otherwise, the matrix is filled by rows.
dimnames: This is optional. It is an attribute for the matrix of length two (
2), giving the respective names of rows and columns of the matrix.
# using the matrix() function to create a matrix mymatrix <- matrix(c(1,2,3,4,5,6), nrow = 2, ncol = 2, byrow = FALSE, dimname = list(c("row1", "row2"), c("Col1", "Col2")) ) # print the matrix mymatrix
It is worth noting and remembering that the
c()function is used to concatenate items together in
To access the items or elements of a matrix, we use the
. Inside this bracket must be two numbers separated by a comma. The first number is simply to specify the row where the element you seek can be found, while the second number is used to specify the column where the element you seek can be found.
The expression above simply means that we are telling
R to return an element which can be found in the first row and in the second column of a matrix.
# creating a 2 by 2 matrix mymatrix <- matrix(c("apple", "banana", "cherry", "orange"), nrow = 2, ncol = 2) # printing the matrix mymatrix # to access row 1 column 2 element of the matrix mymatrix[1, 2]
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