##
expcurve

expcurve —
This opcode implements a formula for generating a normalised exponential curve in range 0 - 1. It is based on the Max / MSP work of Eric Singer (c) 1994.

## Description

Generates an exponential curve in range 0 to 1 of arbitrary steepness.
Steepness index less than 1.0 would result in Not-a-Number
errors and cause unstable behavior so is treated as if it were 1.

The formula used to calculate the curve is:

(exp(x * log(y))-1) / (y-1)

where x is equal to *kindex* and y is equal to *ksteepness*.

## Syntax

kout **expcurve** kindex, ksteepness

## Performance

*kindex* -- Index value. Expected range 0 to 1.

*ksteepness* -- Steepness of the generated curve. Values
closer to 1.0 result in a straighter line while larger values steepen the
curve.

*kout* -- Scaled output.

## Examples

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

**Example 278. Example of the expcurve 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 Silent
-odac -iadc -n ;;;realtime output
</CsOptions>
<CsInstruments>
sr = 44100
ksmps = 1000
nchnls = 2
instr 1 ; logcurve test
kmod phasor 1/p3
kout expcurve kmod, p4
printks "mod = %f out= %f\\n", 0.5, kmod, kout
endin
/*--- ---*/
</CsInstruments>
<CsScore>
i1 0 5 2
i1 5 5 5
i1 10 5 30
i1 15 5 0.5
e
</CsScore>
</CsoundSynthesizer>

## Credits

Author: David Akbari |

October |

2006 |

Range check introduced in 6.16 by John ffitch |