R help - Sep 2009 - Tool for solving equations

Does exist any tool in R to solve equations, especially complex 
exponential equations?
For example:
y = 100*exp(b*(1-exp(c*x))/c)
If it is so, then what is the package i have to
use and what is algorythm for this solving?
Thank you for advance.
With regard, Dmitry.

On Sep 28, 2009, at 6:22 PM, Dmitry Gospodaryov wrote:
> Does exist any tool in R to solve equations, especially complex  
> exponential equations?
> For example:
> y = 100*exp(b*(1-exp(c*x))/c)
> If it is so, then what is the package i have to
> use and what is algorythm for this solving?
> Thank you for advance.
> With regard, Dmitry.
>
You want an analytical solution of 100*exp(b*(1-exp(c*x))/c) = 0 in  
terms of b and c?

library(Ryacas)  # perhaps

Or do you want to specify b and c and get a numerical solution?

?uniroot
?polyroot

Or find the minimum of y?

?nlm  # and others mentioned on that page.

-- 
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

On Sep 28, 2009, at 8:49 PM, David Winsemius wrote:
>
> On Sep 28, 2009, at 6:22 PM, Dmitry Gospodaryov wrote:
>
>> Does exist any tool in R to solve equations, especially complex  
>> exponential equations?
>> For example:
>> y = 100*exp(b*(1-exp(c*x))/c)
If you plot that function, you see that it is asymptotically zero in  
its positive domain:

 > b=10; c=1
 > plot(-10:10, 100*exp(b*(1-exp(c*(-10:10)))/c))
 >  100*exp(b*(1-exp(c*(-10:10)))/c)
  [1]  2.201647e+06  2.199930e+06  2.195270e+06  2.182652e+06   
2.148720e+06  2.059123e+06
  [7]  1.834007e+06  1.338820e+06  5.691034e+05  5.562432e+04   
1.000000e+02  3.448235e-06
[13]  1.789295e-26  1.295885e-81 1.683418e-231  0.000000e+00  0.000000e 
+00  0.000000e+00
[19]  0.000000e+00  0.000000e+00  0.000000e+00

... So that raises the question of what you are really trying to  
accomplish.
>> If it is so, then what is the package i have to
>> use and what is algorythm for this solving?
>> Thank you for advance.
>> With regard, Dmitry.

-- 
David Winsemius, MD
Heritage Laboratories
West Hartford, CT