[R] basic math question?

[Uwe Ligges]

AP05 wrote:
> This seems like it's easy but I can't seem to get it.
>  
>  
> My equation is (a^b)/c = d.
>  
> I know that I can solve for b via
>  
> log(d*c) / log(a) = b
>  
>  
> However, I don't really have d in the first place I have d/sum(d)
> values...no d's...just d/sum(d) values that all add to 1.0
>  
> So, for example, if my data is
>  
> a=4,9,12,3
> b=unknown
> c=12,18,13,20
> d/sum(d)=43,45,23,18

d/sum(d) should indeed add to one, hence I do not understand the data 
above...

If you do not have d (but only d/sum(d)), then you simply cannot 
estimate b in (a^b)/c = d. At least, the solution is not unique.

BTW: In what sense is this related to R(-help)?

Uwe Ligges




>  
> I need an estimate of b. How can I do model and code this?
>  
> Again, b is a power term of a and b^a are divided by c.
>  
> Thank you,
> Jeff
>  
>  
> 
> 
> Checked by AVG Free Edition. 
> 
> PM
>  
> 
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