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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 1/21
pi pi/4 2
-3-3/42
eps 1/2 -51
realmax 1-eps/2 1024
realmin 1/2 -1021

More About

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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.

See Also

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Introduced before R2006a

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