sign

Sign of real or complex value

Syntax

``sign(z)``

Description

example

````sign(z)` returns the sign of real or complex value `z`. The sign of a complex number `z` is defined as `z/abs(z)`. If `z` is a vector or a matrix, `sign(z)` returns the sign of each element of `z`.```

Examples

Signs of Real Numbers

Find the signs of these symbolic real numbers:

`[sign(sym(1/2)), sign(sym(0)), sign(sym(pi) - 4)]`
```ans = [ 1, 0, -1]```

Signs of Matrix Elements

Find the signs of the real and complex elements of matrix `A`:

```A = sym([(1/2 + i), -25; i*(i + 1), pi/6 - i*pi/2]); sign(A)```
```ans = [ 5^(1/2)*(1/5 + 2i/5), -1] [ 2^(1/2)*(- 1/2 + 1i/2), 5^(1/2)*18^(1/2)*(1/30 - 1i/10)]```

Sign of Symbolic Expression

Find the sign of this expression assuming that the value `x` is negative:

```syms x assume(x < 0) sign(5*x^3)```
```ans = -1```

For further computations, clear the assumption on `x` by recreating it using `syms`:

`syms x`

Input Arguments

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Input specified as a symbolic number, variable, expression, function, vector, or matrix.

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Sign Function

The sign function of any number z is defined via the absolute value of z:

`$\mathrm{sign}\left(z\right)=\frac{z}{|z|}$`

Thus, the sign function of a real number z can be defined as follows:

Tips

• Calling `sign` for a number that is not a symbolic object invokes the MATLAB® `sign` function.

Version History

Introduced in R2013a