The Alternative Csound Reference Manual
Previous |  | Next

# 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 files logbtwo.orc and logbtwo.sco.

Example 1. Example of the logbtwo opcode.

    /* logbtwo.orc */
    /* Written by Kevin Conder */
    ; Initialize the global variables.
    sr = 44100
    kr = 4410
    ksmps = 10
    nchnls = 1

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

    /* logbtwo.sco */
    /* Written by Kevin Conder */
    ; Play Instrument #1 for one second.
    i 1 0 1
    e
    /* logbtwo.sco */

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

New in Csound version 3.57

Previous | Home | Next
log10 | Up | loopseg