logbtwo
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## logbtwo

logbtwo — Performs a logarithmic base two calculation.

## Description

Performs a logarithmic base two calculation.

## Syntax

    logbtwo(x)  (init-rate or control-rate args only)

## Performance

logbtwo() returns the logarithm base two of x. The range of values admitted as argument is .25 to 4 (i.e. from -2 octave to +2 octave response). This function is the inverse of powoftwo().

These functions are fast, because they read values stored in tables. Also they are very useful when working with tuning ratios. They work at i- and k-rate.

## Examples

Here is an example of the logbtwo opcode. It uses the file logbtwo.csd.

Example 245. Example of the logbtwo opcode.

See the sections Real-time Audio and Command Line Flags for more information on using command line flags.

    <CsoundSynthesizer>
    <CsOptions>
    ; Select audio/midi flags here according to platform
    ; Audio out   Audio in
    -odac           -iadc    ;;;RT audio I/O
    ; For Non-realtime ouput leave only the line below:
    ; -o logbtwo.wav -W ;;; for file output any platform
    </CsOptions>
    <CsInstruments>

    ; Initialize the global variables.
    sr = 44100
    kr = 4410
    ksmps = 10
    nchnls = 1

    ; Instrument #1.
    instr 1
      i1 = logbtwo(3)
      print i1
    endin

    </CsInstruments>
    <CsScore>

    ; Play Instrument #1 for one second.
    i 1 0 1
    e

    </CsScore>
    </CsoundSynthesizer>

Its output should include a line like this:

    instr 1:  i1 = 1.585

## See Also

powoftwo

## Credits

Author: Gabriel Maldonado
Italy
June 1998

Author: John ffitch
University of Bath, Codemist, Ltd.
Bath, UK
July 1999

Example written by Kevin Conder.

New in Csound version 3.57

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