gives the base-2 logarithm of x.


  • Mathematical function, suitable for both symbolic and numerical manipulation.
  • Log2 gives exact integer or rational number results when possible.
  • For certain special arguments, Log2 automatically evaluates to exact values.
  • Log2 can be evaluated to arbitrary numerical precision.
  • Log2 automatically threads over lists.


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Basic Examples  (5)

Log2 gives the logarithm to base 2:

Plot over a subset of the reals:

Plot over a subset of the complexes:

Series expansion shifted from the origin:

Asymptotic expansion at a singular point:

Scope  (36)

Numerical Evaluation  (6)

Evaluate numerically:

Evaluate to high precision:

The precision of the output tracks the precision of the input:

Complex number inputs:

Evaluate efficiently at high precision:

Log2 can deal with realvalued intervals:

Log2 threads elementwise over lists and matrices:

Specific Values  (6)

Values of Log2 at fixed points:

Values at zero:

Values at infinity:

Zero argument gives a symbolic result:

Zero of Log2:

Find a value of x for which the Log2[x]=0.5:

Visualization  (3)

Plot the Log2 function:

Plot the real part of :

Plot the imaginary part of :

Polar plot with :

Function Properties  (4)

Log2 is defined for all positive values:

Log2 is defined for all nonzero complex values:

Function range of Log2:

Log2 has a branch cut along the negative real axis:

TraditionalForm formatting:

Differentiation  (3)

First derivative:

Higher derivatives:

Plot the higher derivatives:

Formula for the ^(th) derivative:

Integration  (3)

Compute the indefinite integral using Integrate:

Definite integral of Log2:

More integrals:

Series Expansions  (5)

Find the Taylor expansion using Series:

Plots of the first three approximations around :

General term in the series expansion using SeriesCoefficient:


Asymptotic expansions at the branch cut:

Log2 can be applied to power series:

Function Identities and Simplifications  (6)

Basic identity for Log2:

Logarithm of a power function simplification:

Simplify logarithms with assumptions:

Logarithm of a product:

Change of base:

Expand assuming real variables x and y:

Applications  (4)

Worst-case complexity of merge sort algorithm from its functional equation:

Best-case complexity of merge sort algorithm:

Bubble sort is asymptotically worse than merge sort:

Find the age of a sample in units of its half-life time:

Compute the number of bits needed to store a large integer:

Compare to the exact result:

Properties & Relations  (2)

Number of bits used to represent the Wolfram Language's machine reals:

Simplification with assumptions:

Introduced in 2008