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rand

Output is a controlled random number series between -amp and +amp

Syntax

ares rand xamp [, iseed] [, isel] [, ioffset]
kres rand xamp [, iseed] [, isel] [, ioffset]

Initialization

iseed (optional, default=0.5) -- a seed value for the recursive pseudo-random formula. A value between 0 and 1 will produce an initial output of kamp * iseed. A value greater than 1 will be seeded from the system clock. A negative value will cause seed re-initialization to be skipped. The default seed value is .5.

isel (optional, default=0) -- if zero, a 16-bit number is generated. If non-zero, a 31-bit random number is generated. Default is 0.

ioffset (optional, default=0) -- a base value added to the random result. New in Csound version 4.03.

Performance

kamp, xamp -- range over which random numbers are distributed.

ares, kres -- Random number produced.

The internal pseudo-random formula produces values which are uniformly distributed over the range kamp to -kamp. rand will thus generate uniform white noise with an R.M.S value of kamp / root 2.

The value ares or kres is within is a half-closed interval which contains -xamp, but never contains +xamp.

Examples

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

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

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

instr 1 ;same values every time

krnd rand 100
     printk .5, krnd                    ; look 
aout oscili 0.8, 440+krnd, 1            ; & listen
     outs aout, aout

endin

instr 2 ;different values every time

krnd rand 100, 10                       ; seed from system clock
     printk .5, krnd                    ; look 
aout oscili 0.8, 440+krnd, 1            ; & listen
     outs aout, aout

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

i 1 0 1
i 2 2 1
e

</CsScore>
</CsoundSynthesizer>

The example will produce the following output:

i   1 time     0.00067:    50.00305
i   1 time     0.50000:    62.71362
i   1 time     1.00000:   -89.31885

WARNING: Seeding from current time 472230558

i   2 time     2.00067:   -70.65735
i   2 time     2.50000:    69.15283
i   2 time     3.00000:   -48.79761

See also

Random (Noise) Generators, randh, randi

Credits

Thanks to a note from John ffitch, I changed the names of the parameters.