In R, a 4 𝗑 2-matrix X can be created with a following command:

> x <- matrix (nrow=4, ncol=2, data=c(1,2,3,4,5,6,7,8) )

> x

[,1] [,2]

[1,] 1 5

[2,] 2 6

[3,] 3 7

[4,] 4 8

We can get specific properties of a matrix:

> dim (x) # tells the

[1] 4 2 dimension of matrix

> nrow (x) # tells

[1] 4 the number of rows

> ncol (x) # tells

[1] 2 the number of columns

> x <- matrix (nrow=4, ncol=2, data=c(1,2,3,4,5,6,7,8) )

> x

[,1] [,2]

[1,] 1 5

[2,] 2 6

[3,] 3 7

[4,] 4 8

**Properties of a Matrix**We can get specific properties of a matrix:

> dim (x) # tells the

[1] 4 2 dimension of matrix

> nrow (x) # tells

[1] 4 the number of rows

> ncol (x) # tells

[1] 2 the number of columns

> mode (x) # Informs the type or storage mode of an object, e.g., numerical, logical etc.

[1] "numeric"

attributes provides all the attributes of an object
> attributes (x) # Informs the dimension of matrix

$dim [1] 4 2

Help on the Object "Matrix"

To know more about these important objects, we use R-help on "matrix".

> help ("matrix")

matrix package:base R Documentation

Matrices

Description :

'matrix' creates a matrix from the given set of values.

'as.matrix' attempts to turn its argument into a matrix.

'is.matrix' tests if its argument is a (strict) matrix. It is generic: you can write methods to handle specific classes of objects, see Internal Methods.

Then we get an overview on how a matrix can be created and what parameters are available:

Usage :

matrix(data [= NA, nrow = 1 , ncol = 1, byrow = FALSE, dimension = NULL)

as.matrix (x)

is. matrix (x)

Arguments :

data: an optional data vector.

nrow: the desired number of rows

ncol: the desired number of columns

byrow: logical. If 'FALSE' (the default) the matrix is filled by columns, otherwise the matrix is filled by rows.

dimnames: A 'dimnames' attribute for the matrix: a 'list' of length 2.

x: an R object.

Finally, references and cross-references are displayed...

References :

Becker, R. A., Chambers, J. M. and wilks, A.

R. (1988) _The New S Language_. wadsworth & Books/Cole.

See Also:

'data.matrix' , which attempts to convert to a numeric matrix.

**.... as well as an example:**

Examples :

is.matrix (as.matrix (1 : 10) )

data (warpbreaks)

! is.matrix(warpbreaks) # data.frame, NOT matrix!

warpbreaks [1 : 10,]

as.matrix(warpbreaks[1 : 10,]) #using

as.matrix.data.frame(.) method

**Matrix Operations**

Assigning a specified number to all matrix elements:

> x <- matrix (nrow=4, ncol=2, data=2 )

> x

[,1] [,2]

[1,] 2 2

[2,] 2 2

[3,] 2 2

[4,] 2 2

Construction of a diagonal matrix, here the identity matrix of a dimension 2:

> d <- diag (1, nrow=2, ncol=2)

> d

[,1] [,2]

[1,] 1 0

[2,] 0 1

**Transpose of a matrix x: x'**

> x <- matrix (nrow=4, ncol=2, data=1:8, byrow=T )

> x

[,1] [,2]

[1,] 1 2

[2,] 3 4

[3,] 5 6

[4,] 7 8

**Multiplication of a matrix with a constant**

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