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urd

A discrete user-defined-distribution random generator that can be used as a function.

Syntax

aout = urd(ktableNum)
iout = urd(itableNum)
kout = urd(ktableNum)

Initialization

itableNum -- number of table containing the random-distribution function. Such table is generated by the user. See GEN40, GEN41, and GEN42. The table length does not need to be a power of 2.

Performance

ktableNum -- number of table containing the random-distribution function. Such table is generated by the user. See GEN40, GEN41, and GEN42. The table length does not need to be a power of 2.

urd is the same opcode as duserrnd, but can be used in function fashion.

For a tutorial about random distribution histograms and functions see:

  • 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 urd opcode. It uses the file urd.csd.

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

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

instr 1 

ktab  = 1                       ;ftable 1
kurd  = urd(ktab) 
ktrig metro 5                   ;triggers 5 times per second
kres  samphold kurd, ktrig      ;sample and hold value of kurd
      printk2 kres              ;print it
asig  poscil .5, 220+kres, 2
      outs asig, asig
endin

instr 2

seed 0  ;every run new values

ktab  = 1                       ;ftable 1
kurd  = urd(ktab) 
ktrig metro 5                   ;triggers 5 times per second
kres  samphold kurd, ktrig      ;sample and hold value of kurd
      printk2 kres              ;print it
asig  poscil .5, 220+kres, 2
      outs asig, asig

endin
</CsInstruments>
<CsScore>
f1 0 -20 -42  10 20 .3 100 200 .7 ;30% choose between 10 and 20 and 70% between 100 and 200
f2 0 8192 10 1                    ;sine wave

i 1 0 5
i 2 6 5
e
</CsScore>
</CsoundSynthesizer>

Its output should include lines like these:

i1   184.61538
i1   130.76923
i1   169.23077
i1    12.00000
.......

WARNING: Seeding from current time 3751086165

i2   138.46154
i2    12.00000
i2   123.07692
i2   161.53846
i2   123.07692
i2   153.84615
......

See also

Random (Noise) Generators

Credits

Author: Gabriel Maldonado

New in Version 4.16