How to treat with logarithm numerically when it becomes negative?
 
  
 
  
 
 
 
 
 
 
    
        
        asked 12 years ago  
 
 ela gravatar image  
 
 
 
 
 
I have a term log(f(x)) in my equations which I am trying to solve them numerically. But the solver does not solve, perhaps when the argument of the logarithm becomes negative. What should I write in the program when f(x)<0 in the loop in order not to loose the iteration?
 
Thanks
 
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I think you have to provide more details.  In general, log of a negative number does make sense, but it is multi-valued.
kcrisman gravatar imagekcrisman (
    
        12 years ago
    )
you mean detail in the program?
ela gravatar imageela (
    
        12 years ago
    )
Have you tried:

find_root(log(x*x-x),-2,0)
   
-0.6180339887498988

 find_root(log(x*x-x),-2,2)
 
1.6180339887498947
achrzesz gravatar imageachrzesz (
    
        12 years ago
    )
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