true

Logical 1 (true)

Syntax

true

T = true(n)

T = true(sz)

T = true(sz1,...,szN)

T = true(___,like=p)

Description

true is shorthand for the logical value 1.

T = true(n) is an n-by-n matrix of logical ones.

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

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

T = true(___,like=p) returns an array of logical ones of the same sparsity as the logical variable p using any of the previous size syntaxes.

Examples

Generate Square Matrix of Logical Ones

Use true to generate a 3-by-3 square matrix of logical ones.

A = true(3)

A = 3×3 logical array

   1   1   1
   1   1   1
   1   1   1

class(A)

ans = 
'logical'

The result is of class logical.

Generate Array of Logical Ones with Arbitrary Dimensions

Use true to generate a 3-by-2-by-2 matrix of logical ones.

true(3,2,2)

ans = 3×2×2 logical array
ans(:,:,1) =

   1   1
   1   1
   1   1


ans(:,:,2) =

   1   1
   1   1
   1   1

Alternatively, you can use a size vector to specify the size of the matrix.

true([3,2,2])

ans = 3×2×2 logical array
ans(:,:,1) =

   1   1
   1   1
   1   1


ans(:,:,2) =

   1   1
   1   1
   1   1

Note that specifying multiple vector inputs returns an error.

Execute Logic Statement

true along with false can be used to execute logic statements.

Test the logical statement

~(A and B) = (~A) or (~B)

for A = true and B = false.

~(true & false) == (~true) | (~false)

ans = logical
   1

The result is logical 1 (true), since the logical statements on both sides of the equation are equivalent. This logical statement is an instance of De Morgan's Law.

Generate Logical Array of Selected Sparsity

Generate a logical array of the same sparsity as the selected array.

A = logical(sparse(5,3));
whos A

  Name      Size            Bytes  Class      Attributes

  A         5x3                41  logical    sparse    

T = true(4,like=A);
whos T

  Name      Size            Bytes  Class      Attributes

  T         4x4               184  logical    sparse    

The output array T has the same sparse attribute and data-type as the specified array A.

Input Arguments

n — Size of square matrix

integer

Size of square matrix, specified as an integer. n sets the output array size to n-by-n. For example, true(3) returns a 3-by-3 array of logical ones.

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

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

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

sz — Size vector

row vector of integers

Size vector, specified as a row vector of integers. For example, true([2 3]) returns a 2-by-3 array of logical ones.

• If the size of any dimension is 0, then T 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, T, does not include those dimensions.

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

sz1,...,szN — Size inputs

comma-separated list of integers

Size inputs, specified by a comma-separated list of integers. For example, true(2,3) returns a 2-by-3 array of logical ones.

• If the size of any dimension is 0, then T 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, T, does not include those dimensions.

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

p — Prototype

logical variable

Prototype, specified as a logical variable.

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

Output Arguments

T — Output of logical ones

scalar | vector | matrix | N-D array

Output of logical ones, returned as a scalar, vector, matrix, or N-D array.

Data Types: logical

Tips

• true(n) is much faster and more memory efficient than logical(true(n)).

Extended Capabilities

C/C++ Code Generation

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

Usage notes and limitations:

• Dimensions must be real, nonnegative, integers.

GPU Code Generation

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

Usage notes and limitations:

• 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 true 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).

Distributed Arrays

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

Usage notes and limitations:

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

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

Version History

Introduced before R2006a