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 Minimization of expression for a parameter

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T O P I C    R E V I E W
shag Posted - 06/24/2015 : 09:57:31 AM
Origin Ver. and Service Release (Select Help-->About Origin): v8.0724
Operating System: Windows 8

I have two complicated functions which can be represented as A = f(B) and C = f(A). Where C is a summation of terms, each having the unknown parameter B. I want to find the value of parameter B, for which C has the minimum value. Please help me how to go about it. As both the functions are pretty complicated, they are not available in origin and need to be defined.
thanks
3   L A T E S T    R E P L I E S    (Newest First)
SeanMao Posted - 06/28/2015 : 10:30:30 PM
Hi,

I plotted your C function over D from 10^-26 to 10^-19, and there seems no minimum but a maximum:




If you want to find the maximum, you can first calculate the derivative and find where the derivative closest to 0.

Regards!

Sean
shag Posted - 06/27/2015 : 07:24:56 AM
Dear Sean
Thanks for the response. As you said, I tried to calculate C as a function of B. Following is the function.

C = 1/3 (-11.6202 + (
1.25 (1.99706 + E^(2.41371*10^20 (-6.0924*10^-24 - D))))/(
1.99633 + E^(3.01714*10^20 (-6.0924*10^-24 - D))) + (
1.66667 (1.99706 + E^(2.41371*10^20 (-6.0924*10^-24 - D))))/(
1.99511 + E^(4.02285*10^20 (-6.0924*10^-24 - D))) + (
2.5 (1.99706 + E^(2.41371*10^20 (-6.0924*10^-24 - D))))/(
1.99267 + E^(6.03427*10^20 (-6.0924*10^-24 - D))))


In this expression, D is the only unknown. I want to find the positive value of D for which function C has minima.

thanks

quote:
Originally posted by SeanMao

Hi,

What kind of data do you have? Can you calculate C value if given a certain B value? Or you want to do symbolic calculation?

You need to provide more details so that we can try to help.

Regards!

Sean

OriginLab Tech. Service
SeanMao Posted - 06/25/2015 : 03:13:10 AM
Hi,

What kind of data do you have? Can you calculate C value if given a certain B value? Or you want to do symbolic calculation?

You need to provide more details so that we can try to help.

Regards!

Sean

OriginLab Tech. Service

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