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betarand

Beta distribution random number generator (positive values only).

This is an x-class noise generator.

Syntax

ares betarand krange, kalpha, kbeta
ires betarand krange, kalpha, kbeta
kres betarand krange, kalpha, kbeta

Performance

krange -- range of the random numbers (0 - krange).

kalpha -- alpha value. If kalpha is smaller than one, smaller values favor values near 0.

kbeta -- beta value. If kbeta is smaller than one, smaller values favor values near krange.

If both kalpha and kbeta equal one we have uniform distribution. If both kalpha and kbeta are greater than one we have a sort of Gaussian distribution. Outputs only positive numbers.

For more detailed explanation of these distributions, see:

  1. C. Dodge - T.A. Jerse 1985. Computer music. Schirmer books. pp.265 - 286
  2. D. Lorrain. A panoply of stochastic cannons. In C. Roads, ed. 1989. Music machine. Cambridge, Massachusetts: MIT press, pp. 351 - 379.

Examples

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

Example of the betarand opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac     ;;;RT audio out
;-iadc    ;;;uncomment -iadc if RT audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o betarand.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 32
nchnls = 2
0dbfs = 1

instr 1         ; every run time same values

kbeta   betarand 100, 1, 1
        printk .2, kbeta                ; look 
aout    oscili 0.8, 440+kbeta, 1        ; & listen
        outs    aout, aout
endin

instr 2         ; every run time different values

        seed 0
kbeta   betarand 100, 1, 1
        printk .2, kbeta                ; look 
aout    oscili 0.8, 440+kbeta, 1        ; & listen
        outs    aout, aout
endin

</CsInstruments>
<CsScore>
; sine wave
f 1 0 16384 10 1

i 1 0 2
i 2 3 2
e

</CsScore>
</CsoundSynthesizer>

Its output should include a line like:

i   1 time     0.00267:    85.74227
i   1 time     0.20267:    12.07606
i   1 time     0.40267:    25.03239
i   1 time     0.60267:     0.42037
i   1 time     0.80267:    76.69589
i   1 time     1.00000:    29.73339
i   1 time     1.20267:    48.29811
i   1 time     1.40267:    75.46507
i   1 time     1.60267:    74.80686
i   1 time     1.80000:    81.37473
i   1 time     2.00000:    55.48827
Seeding from current time 3472120656
i   2 time     3.00267:    57.21408
i   2 time     3.20267:    30.95705
i   2 time     3.40267:    19.71687
i   2 time     3.60000:    64.48965
i   2 time     3.80267:    72.35818
i   2 time     4.00000:    49.65395
i   2 time     4.20000:    55.25888
i   2 time     4.40267:     3.98308
i   2 time     4.60267:    52.98075
i   2 time     4.80267:    58.07925
i   2 time     5.00000:    56.38914

See also

Random (Noise) Generators

Credits

Author: Paris Smaragdis
MIT, Cambridge
1995

Existed in 3.30