log2

Purpose

Dissect floating-point numbers.

Synopsis

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

Description

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

[F,E] = log2(X) for a real matrix X, returns a matrix F of real numbers, usually in the range 0.5 <= abs(F) < 1, and a matrix E of integers, so that X = F.* 2.^E. Any zeros in X produce F = 0 and E = 0.

This function corresponds to the ANSI C function frexp() and the IEEE floating-point standard function logb().

Examples

For IEEE arithmetic, the statement [F,E] = log2(X) yields the following 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

format hex, log, pow2, realmax, realmin

(c) Copyright 1994 by The MathWorks, Inc.