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log2

Base 2 logarithm and dissect floating-point numbers into exponent and mantissa

Syntax

`Y = log2(X)[F,E] = log2(X)`

Description

`Y = log2(X)` computes the base 2 logarithm of the elements of `X`.

`[F,E] = log2(X)` returns arrays `F` and `E`. Argument `F` is an array of real values, usually in the range ```0.5 <= abs(F) < 1```. For real `X`, `F` satisfies the equation: `X = F.*2.^E`. Argument `E` is an array of integers that, for real `X`, satisfy the equation: `X = F.*2.^E`.

Examples

For IEEE® arithmetic, the statement `[F,E] = log2(X)` yields the values:

X

F

E

`1 ``1/2``1`
`pi ``pi/4 ``2`
` -3``-3/4``2`
`eps ``1/2 ``-51`
`realmax ``1-eps/2 ``1024`
`realmin ``1/2 ``-1021`

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Tall Array Support

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

Tips

This function corresponds to the ANSI® C function `frexp()` and the IEEE floating-point standard function `logb()`. Any zeros in `X` produce `F = 0` and `E = 0`.