repelem - Repeat copies of array elements - MATLAB (original) (raw)

Repeat copies of array elements

Syntax

Description

[u](#bum31rc-1-u) = repelem([v](#bum31rc-1-v),[n](#bum31rc-1-n)), where v is a scalar or vector, returns a vector of repeated elements of v.

If n is a scalar, then each element of v is repeated n times. The length of u is length(v)*n.
If n is a vector, then it must be the same length as v. Each element of n specifies the number of times to repeat the corresponding element of v.

This syntax is not supported for table input.

example

[B](#bum31rc-1-B) = repelem([A](#bum31rc-1-A),[r1,...,rN](#bum31rc-1-r1rN)) returns an array with each element of A repeated according to r1,...,rN. Each r1,...,rN must either be a scalar or a vector with the same length as A in the corresponding dimension. For example, if A is a matrix, repelem(A,2,3) returns a matrix containing a 2-by-3 block of each element of A.

example

Examples

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Create a vector and repeat each of its elements three times into a new vector.

v = [1 2 3 4]; u = repelem(v,3)

u = 1×12

 1     1     1     2     2     2     3     3     3     4     4     4

Repeat the first two elements of v twice and the last two elements three times.

u = 1×10

 1     1     2     2     3     3     3     4     4     4

Create a matrix and repeat each element into a 3-by-2 block of a new matrix.

B = 6×4

 1     1     2     2
 1     1     2     2
 1     1     2     2
 3     3     4     4
 3     3     4     4
 3     3     4     4

Create a matrix and copy its columns into a new array, repeating the first column twice and second column three times.

B = 2×5

 1     1     2     2     2
 3     3     4     4     4

Create two column vectors.

A = [1; 3; 5]; B = [2; 4];

Generate all element combinations of the two vectors by using repelem and repmat. Each row of the output T is a combination with the first element coming from the first vector and the second element coming from the second vector. This command is equivalent to finding the Cartesian product of two vectors.

T = [repelem(A,numel(B)) repmat(B,numel(A),1)]

T = 6×2

Starting in R2023a, you can also use the combinations function to generate all element combinations of two vectors.

T=6×2 table A B _ _

Input Arguments

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Input element, specified as a scalar or a vector.

Number of times to repeat each element, specified as a scalar or a vector. If n is a scalar, then all elements of v are repeated n times. If n is a vector, then each element of n specifies the number of times to repeat the corresponding element of v. In either case, n must be integer-valued.

Input array, specified as a matrix or multidimensional array.

Repetition factors for each dimension, specified as separate arguments of integer-valued scalars or vectors. If A is a table, each repetition factor must be a scalar.

Output Arguments

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Output vector. If v is a row vector or scalar, u is a row vector. If v is a column vector, u is also a column vector.

Output array, returned as a matrix or multidimensional array.

Extended Capabilities

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This function supports tall arrays with the limitations:

The two-input syntax is not supported.
The replication factor in the first dimension must be 1. For example, repelem(TA,1,n,p,...).

For more information, see Tall Arrays.

Usage notes and limitations:

The input must be a vector or matrix. The input cannot be a multidimensional array.

Usage notes and limitations:

The input must be a vector or matrix. The input cannot be a multidimensional array.

The repelem function fully supports GPU arrays. To run the function on a GPU, specify the input data as a gpuArray (Parallel Computing Toolbox). For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced in R2015a