ones

Create array of all ones

Syntax

X = ones

X = ones(n)

X = ones(sz1,...,szN)

X = ones(sz)

X = ones(___,typename)

X = ones(___,'like',p)

Description

X = ones returns the scalar 1.

X = ones(n) returns an n-by-n matrix of ones.

X = ones(sz1,...,szN) returns an sz1-by-...-by-szN array of ones where sz1,...,szN indicates the size of each dimension. For example, ones(2,3) returns a 2-by-3 array of ones.

X = ones(sz) returns an array of ones where the size vector, sz, defines size(X). For example, ones([2,3]) returns a 2-by-3 array of ones.

X = ones(___,typename) also specifies the data type (class) of X for any of the previous syntaxes. For example, ones(5,'int8') returns a 5-by-5 matrix of 8-bit integers.

X = ones(___,'like',p) specifies that X has the same data type, sparsity, and complexity (real or complex) as the numeric variable p.

Examples

Square Array of Ones

Create a 4-by-4 array of ones.

X = ones(4)

X = 4×4

     1     1     1     1
     1     1     1     1
     1     1     1     1
     1     1     1     1

3-D Array of Ones

Create a 2-by-3-by-4 array of ones.

X = ones(2,3,4);

size(X)

ans = 1×3

     2     3     4

Size Defined by Existing Array

Define a 3-by-2 array A.

A = [1 4 ; 2 5 ; 3 6];

sz = size(A)

sz = 1×2

     3     2

Create an array of ones that is the same size as A.

X = ones(sz)

X = 3×2

     1     1
     1     1
     1     1

Nondefault Numeric Data Type

Create a 1-by-3 vector of ones whose elements are 16-bit unsigned integers.

X = ones(1,3,'uint16'),

X = 1x3 uint16 row vector

   1   1   1

class(X)

ans = 
'uint16'

Complex One

Create a scalar 1 that is not real valued, but instead is complex like an existing array.

Define a complex vector.

p = [1+2i 3i];

Create a scalar 1 that is complex like p.

X = ones('like',p)

X = 
1.0000 + 0.0000i

Size and Numeric Data Type Defined by Existing Array

Define a 2-by-3 array of 8-bit unsigned integers.

p = uint8([1 3 5 ; 2 4 6]);

Create an array of ones that is the same size and data type as p.

X = ones(size(p),'like',p),

X = 2x3 uint8 matrix

   1   1   1
   1   1   1

class(X)

ans = 
'uint8'

Input Arguments

n — Size of square matrix

integer value

Size of square matrix, specified as an integer value, defines the output as a square, n-by-n matrix of ones.

• If n is 0, then X is an empty matrix.

• If n is negative, then it is treated as 0.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

sz1,...,szN — Size of each dimension

two or more integer values

Size of each dimension, specified as two or more integer values, defines X as a sz1-by...-by-szN array.

• If the size of any dimension is 0, then X is an empty array.

• If the size of any dimension is negative, then it is treated as 0.

• If any trailing dimensions greater than 2 have a size of 1, then the output, X, does not include those dimensions.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

sz — Output size

row vector of integer values

Output size, specified as a row vector of integer values. Each element of this vector indicates the size of the corresponding dimension.

• If the size of any dimension is 0, then X is an empty array.

• If the size of any dimension is negative, then it is treated as 0.

• If any trailing dimensions greater than 2 have a size of 1, then the output, X, does not include those dimensions.

Example: sz = [2 3 4] defines X as a 2-by-3-by-4 array.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

typename — Output class

'double' (default) | 'single' | 'logical' | 'int8' | 'uint8' | ...

Output class, specified as 'double', 'single', 'logical', 'int8', 'uint8', 'int16', 'uint16', 'int32', 'uint32', 'int64', or 'uint64'.

p — Prototype

variable

Prototype, specified as a variable.

Data Types: double | single | logical | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64
Complex Number Support: Yes

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Dimensions must be real, nonnegative integers. Empty dimensions are not supported.

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

Refer to the usage notes and limitations in the C/C++ Code Generation section. The same limitations apply to GPU code generation.

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

Dimensions must be real, nonnegative integers.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

The ones function supports GPU array input with these usage notes and limitations:

• You can specify typename as 'gpuArray'. If you specify typename as 'gpuArray', the default underlying type of the array is double.

  To create a GPU array with underlying type datatype, specify the underlying type as an additional argument before typename. For example, X = ones(3,datatype,'gpuArray') creates a 3-by-3 GPU array of ones with underlying type datatype.

  You can specify the underlying type datatype as one of these options:

  • 'double'

  • 'single'

  • 'logical'

  • 'int8'

  • 'uint8'

  • 'int16'

  • 'uint16'

  • 'int32'

  • 'uint32'

  • 'int64'

  • 'uint64'

• You can also specify the numeric variable p as a gpuArray.

  If you specify p as a gpuArray, the underlying type of the returned array is the same as p.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

Usage notes and limitations:

• You can specify typename as 'codistributed' or 'distributed'. If you specify typename as 'codistributed' or 'distributed', the default underlying type of the returned array is double.

  To create a distributed or codistributed array with underlying type datatype, specify the underlying type as an additional argument before typename. For example, X = ones(3,datatype,'distributed') creates a 3-by-3 distributed matrix of ones with underlying type datatype.

  You can specify the underlying type datatype as one of these options:

  • 'double'

  • 'single'

  • 'logical'

  • 'int8'

  • 'uint8'

  • 'int16'

  • 'uint16'

  • 'int32'

  • 'uint32'

  • 'int64'

  • 'uint64'

• You can also specify p as a codistributed or distributed array.

  If you specify p as a codistributed or distributed array, the underlying type of the returned array is the same as p.

• For additional codistributed syntaxes, see ones (codistributed) (Parallel Computing Toolbox).

For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced before R2006a