log2 函数

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log2 函数

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

以2位基底的对数和解析浮点数值到指数和尾数。

Syntax

语法

Y = log2(X)

[F,E] = log2(X)

Description

描述

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

Y=log2(X)计算X的元素以2为基底的对数。

[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.

[F,E]=log2(X)返回阵列F和E。自变量F是一个实数的阵列，通常在区间0.5 <= abs(F) < 1。实数X，F满足方程：X=F.*2.^E。自变量E是一个整数阵列，实际X，满足方程：X=F.*2.^E。

Remarks

备注

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.

函数相当于ANSI C函数frexp()和IEEE浮点标准函数logb()。X中的任何零，结果F=0和E=0。

Examples

例如

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

计算IEEE运算，算式[F,E]=log2(X)得到的值：

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