sign

Y = sign( x ) returns an array Y the same size as x , where each element of Y is:

• 1 if the corresponding element of x is greater than 0 .
• 0 if the corresponding element of x equals 0 .
• -1 if the corresponding element of x is less than 0 .
• x./abs(x) if x is complex.

Examples

Find Sign Function

Find the sign function of a number.

sign(2)

ans = 1

Find the sign function of the values of a vector.

V = [-11 0 1.5 Inf NaN]; sign(V)

ans = 1×5 -1 0 1 1 NaN

Find the sign function of the values of a matrix.

M = magic(3) - 5; sign(M)

ans = 3×3 1 -1 1 -1 0 1 -1 1 -1

Find the sign function of a complex number.

z = 4 - 3*i; sign(z)

ans = 0.8000 - 0.6000i

Plot Sign Function

Plot the sign function and show its behavior at the zero-crossing. Use eps to represent values just above and below 0 .

x = [-5 -eps(1) 0 eps(1) 5]; y = sign(x); plot(x,y) ylim([-2 2]) grid on

Plot Real and Imaginary Parts of Sign Function

Plot real and imaginary parts of the sign function over - 3 < x < - 3 and - 3 < y < 3 .

v = -3:0.1:3; [x, y] = meshgrid(v); z = x + 1i*y;

Find the real and imaginary parts of the sign function of z .

s = sign(z); re = real(s); im = imag(s);

Plot the real and imaginary parts.

surf(x,y,re) title('Real part of sign function') xlabel('x') ylabel('y')

ylabel y contains an object of type surface." width="583" />

figure(2) surf(x,y,im) title('Imaginary part of sign function') xlabel('x') ylabel('y')

ylabel y contains an object of type surface." width="583" />

Input Arguments

x — Input
scalar | vector | matrix | multidimensional array

Input, specified as a scalar, vector, matrix, or multidimensional array.

If an element of x is NaN , then sign returns NaN in the corresponding element of the output.

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

Extended Capabilities

Tall Arrays
Calculate with arrays that have more rows than fit in memory.

The sign function fully supports tall arrays. For more information, see Tall Arrays.

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

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 sign 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™.

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox) .

Version History

Introduced before R2006a