What is R Matrix and Matrix Function in R? First of all, let’s revise what are matrices. A matrix is a two-dimensional rectangular data set. Thus it can be created using vector input into the matrix function. Also, a matrix is a collection of numbers arranged into a fixed number of rows and columns. The numbers present in the matrix are real. 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. RDocumentation R Enterprise Training. Matrices are the R objects in which the elements are arranged in a two-dimensional rectangular layout. They contain elements of the same atomic types. Though we can create a matrix containing only characters or only logical values, they are not of much use. We use matrices containing numeric elements to be used in mathematical calculations. The R program (as a text file) for the code on this page. In order to see more than just the results from the computations of the functions (i.e. If you want to see the functions echoed back in console as they are processed) use the echo=T option in the source function when running the program.
- Matrix Of Ones In R
- Create Identity Matrix In R
- Create A Simple Matrix
- Transpose Matrix In R
- Create Covariance Matrix In R
- R Data Frame To Matrix
- Create Matrix In R With Column Names
A matrix in R is a two-dimensional rectangular data set and thus it can be created using vector input to the matrix function. It is similar to vector but additionally contains the dimension attribute.
Listof most common functions for creating matrix:
FunctionDescriptionExample
cbind(a,b, c) Combine vectors ascolumns in a matrix cbind(1:5,6:10, 11:15)
rbind(a,b, c) Combine vectors as rows in a matrix rbind(1:5, 6:10, 11:15)
matrix(x,nrow, Create a matrix from a vector x matrix(x = 1:12, nrow =3, ncol = 4)
ncol, byrow)
Wecreate a new matrix with usage of matrix() method. It can take one or morearguments. One that is necessary is list of values which will be contained inmatrix, and other two that are optional are nrow and ncol which representnumber of rows and columns.
Wecan specify names of rows and column, but we must provide argument aboutdimensions of a matrix:
x <- matrix(1:9, ncol= 3, dimnames =list(c(“X”,”Y”,”Z”), c(“A”,”B”,”C”)))
x
A B C
X 1 4 7
Y 2 5 8
Z 3 6 9
Matricescan either contain numbers or character vectors, not both!. If you try tocreate a matrix with both numbers and characters, it will turn all the numbersinto characters:
cbind(c(1,2, 3, 4, 5),
c(“a”, “b”,“c”, “d”, “e”))
[,1] [,2]
[1,] “1” “a”
[2,] “2” “b”
[3,] “3” “c”
[4,] “4” “d”
[5,] “5” “e”
Thematrix() function creates a matrix form a single vector of data. The functionhas 4 main inputs: data – a vector of data, nrow – the number of rows you wantin the matrix, and ncol – the number of columns you want in the matrix, andbyrow – a logical value indicating whether you want to fill the matrix by rows.
Matrix Of Ones In R
Checkout the help menu for the matrix function (?matrix) to see some additionalinputs. Let’s use the matrix() function to re-create a matrix containing thevalues from 1 to 10.
Createa matrix of the integers 1:10, with 5rows and 2 columns:
matrix(data= 1:10,
nrow = 5,
ncol = 2)
[,1] [,2]
[1,] 1 6
Create Identity Matrix In R
[2,] 2 7
[3,] 3 8
[4,] 4 9
[5,] 5 10
Nowwith 2 rows and 5 columns:
matrix(data= 1:10,
nrow = 2,
ncol = 5)
[,1] [,2] [,3] [,4] [,5]
[1,] 1 3 5 7 9
[2,] 2 4 6 8 10
Nowwith 2 rows and 5 columns, but fill by row instead of columns:
matrix(data = 1:10,
nrow = 2,
ncol = 5,
byrow = TRUE)
[,1] [,2] [,3] [,4] [,5]
[1,] 1 2 3 4 5
[2,] 6 7 8 9 10
Wecan change names of rows and columns which are already defined:
x <-matrix(1:9, ncol= 3, dimnames =list(c(“X”,”Y”,”Z”),c(“A”,”B”,”C”)))
x
A B C
X 1 4 7
Y 2 5 8
Z 3 6 9
colnames(x) <- c(“Col1″,”Col2″,”Col3”)
x
Col1 Col2 Col3
X 1 4 7
Y 2 5 8
Z 3 6 9
Tochange row names, use rownames(x) in same way.
Wecan also use cbind() and rbind() to concatenate rows and columns in creating amatrix:
x <- cbind(c(1,2,3), c(7,8,9))
x
[,1] [,2]
[1,] 1 7
[2,] 2 8
[3,] 3 9
rbind()will put 1 2 3 on first row and 7 8 9 on second row:
x <-rbind(c(1,2,3), c(7,8,9))
x
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 7 8 9
cbind()and rbind() both create matrices by combining several vectors of the samelength. cbind() combines vectors as columns, while rbind() combines them asrows.
Let’suse these functions to create a matrix with the numbers 1 through 30. First,we’ll create three vectors of length 5, then we’ll combine them into onematrix. As you will see, the cbind() function will combine the vectors ascolumns in the final matrix, while the rbind() function will combine them asrows.
x <- 1:5
y <- 6:10
z <-11:15
Createa matrix where x, y and z are columns:
cbind(x, y,z)
x y z
[1,] 1 6 11
[2,] 2 7 12
[3,] 3 8 13
[4,] 4 9 14
Create A Simple Matrix
[5,] 5 10 15
Createa matrix where x, y and z are rows
rbind(x, y,z)
[,1] [,2] [,3] [,4] [,5]
x 1 2 3 4 5
y 6 7 8 9 10
z 11 12 13 14 15
Finaly,you can create a matrix using dim() method:
elements <- c(1,2,3,4,5,6,7,8,9)
dim(elements)<-c(3,3)
elements
[,1] [,2] [,3]
![Create Matrix In R Create Matrix In R](https://motogadget.com/shop/media/catalog/product/cache/2/image/9df78eab33525d08d6e5fb8d27136e95/m/s/msp_r9t_12_800.jpg)
[1,] 1 4 7
[2,] 2 5 8
![How How](https://c1.staticflickr.com/5/4073/4905512293_cdf5e74d94_b.jpg)
[3,] 3 6 9
Wehave seen basic methods and ways of creating the matrix. You can also combinethose functions with others.
For example, you can use seq() function in creating amatrix:
x <- matrix(seq(1,10,2),nrow=3)
x
[,1] [,2]
[1,] 1 7
[2,] 3 9
[3,] 5 1
We specified numbers from 1 to 10, with 2 as a steppingstone. You notice how we didn’t get 11 after 9, but 1? That is because matrix()function needs to fill all fields in making a matrix, it can’t leave emptyspace as one might expect.
You can put conditions on which elements will be in yourmatrix. For example, lets see how to put only even numbers from 1-9 list:
our_row <- c(1,2,3,4,5,6,7,8,9)
our_matrix <-matrix(our_row[our_row%%20], nrow=2)
our_matrix
[,1] [,2]
[1,] 2 6
[2,] 4 8
Create a matrix only with numbers which are higher than5:
our_row <- c(1,2,3,4,5,6,7,8,9)
Transpose Matrix In R
our_matrix <- matrix(our_row[our_row>5], nrow=1)
our_matrix
[,1] [,2] [,3]
[1,] 6 7 8
In the same way, you can create matrix which containcharacters:
our_row <- c(“first”,”second”,”third”,”fourth”,”fifth”,”sixth”)
our_matrix <- matrix(our_row,nrow=1) Fiddler download.
our_matrix
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] “first” “second” “third”“fourth” “fifth” “sixth”
You can useconditionals, just like we did on numeric matrix:
our_countries <-c(“China”,”France”,”India”,”Venezuela”,”Argentina”)
asia <- c(“China”,”India”)
our_matrix <- matrix(our_countries[our_countries %in% asia], nrow=1)
our_matrix
[,1] [,2]
[1,] “China” “India”
These were the most common ways of creating a matrix. Ifyou want to learn more about different operations you can do on matrix, pleasecheck out our tutorial, Matrices and operations with them.
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When we create a matrix in R, the row names and column names are not defined but we can define them separately. If we want to take a subset of rows of a matrix then row numbers can be used within single square brackets but if we want to do it with the names then we need to specify those names.