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optimize in very small values

3 messages · Uwe Ligges, Troels Ring

Original
Troels Ring
# 
I hope you will forgive me this simple question on titration.
I'm trying to find very small values from the algorithm below, which I 
believe is
correctly formatted, and the constants are also correct. When SID goes over 
ATOT, fitted vales are
much too low compared to the literature. I guess I must be using optimize 
in a wrong way but cannot find out how to improve it. I'm on windows, R 
2.0. Best wishes
Troels Ring, Aalborg

ATOT <- 0.019
KA <- 3e-7
KW <- 4.4e-14
SID <- 0.01

ff <- function(H,KA,SID,ATOT)
{H^3 + (KA+SID)*H^2+(KA*(SID-ATOT)-KW)*H- KA*KW}
-log10(optimize(ff,c(0,.1),tol=.Machine$double.eps,KA=KA,SID=SID,ATOT=ATOT)$minimum)
Uwe Ligges
#
Troels Ring wrote:

            

      
      
      
    

        
Well, whether the usage is appropriate depends on the problem. At least 
I have not understood what you are going to minimize...

Uwe Ligges

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Troels Ring
    

    

      
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Dear friends - just to prevent further loss of time on the problem below - 
I realized that it was really a root finding exercise and not a 
minimization - uniroot solved the problem.
Sorry for the confusion.
Best wishes
Troels

        
At 00:06 11/23/04, you wrote: