MATLAB Functions Help Desk

log2

Purpose

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

Syntax

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.

Remarks

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.

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

See Also

log         Natural logarithm

pow2        Base 2 power and scale floating-point numbers



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