log2 (MATLAB Functions)

MATLAB Function Reference

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.

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

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, pow2

log1p logical