hi all,

I have this math transformation: numbers from a to b becomes to numbers from c to d, where d goes exponential higher.

for example: I need to make [expr] object, and when I send 1 it outputs 1 when 10 output 1000

m*exp(n*$f1)
where
m=c^(b/(b-a))/d^(a/(b-a)), n=log(d/c)/(b-a)

this is the math but I don't know how to put it in [expr] object

can anyone help

Since calculating m and n should probably be done once (or just when a, b, c, or d is changed), it would be more efficient to just stick them in separate [expr]s and feed those into [expr $f2*exp($f3*$f1)].

To do exponents, use the pow() function in [expr]. $f1^$f2 would be [expr pow($f1, $f2)]

As for the log, it depends on what the base is. log() in [expr] is base e (natural logarithm), but there is also log10() for a base 10 logarithm.

There is a url in the helpfile for [expr] to a webpage listing all the functions built into it. It doesn't have full descriptions on the functions themselves, but they're all based on C expressions, so any website describing the C function for pow(), for example, should be relevant.

!thanks:)