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segovi01
Mexico
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 Posted - 10/06/2006 : 2:34:00 PM
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Origin Version (Select Help-->About Origin): 7.5pro
Operating System: windows xp
Hi All
im trying to fit data which generates a S shape graphic to a equation
of Y=(A0+B0)/(1+(A0/B0)exp(-k(A0+B0)X))
with just one parameter to be fitted, k, A0 and B0 are both constants and their value dont need to be fitted
since im not familiar with origin c i do not know how to program this in origin, could any body help me
thank you
Sincerely
Jose
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Mike Buess
USA
3037 Posts |
Posted - 10/07/2006 : 08:03:30 AM
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Hi Jose,
Learn about the fitting procedure by starting with the Advanced Fitting Tool topic here...
Help > Tutorials > Origin Tutorials > Tutorial 11
You can use Origin's built-in SLogistic3 function in the Growth/Sigmoidal category which is defined as y=a/(1+b*exp(-k*x)). Start by fixing a to A0+B0 and b to A0/B0 and divide the final value of k by A0+B0.
Mike Buess
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segovi01
Mexico
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Posted - 10/23/2006 : 06:41:35 AM
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thank you for your response, but my equation is Y=(A0+B0)/(1+(A0/B0)exp(-k(A0+B0)X))
and the
SLogistic3 function in the Growth/Sigmoidal is y=a/(1+b*exp(-k*x))
and it would be true just when A0+B0=1, i can fit using this because and need to modify in order to obtain y=a/(1+b*exp(-k*a*x))
that would be what i need, how can i do that??
thank you
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Mike Buess
USA
3037 Posts |
Posted - 10/23/2006 : 07:37:02 AM
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quote:
...it would be true just when A0+B0=1
As I said above, just divide the value of k obtained with SLogistic3 by A0+B0 to get your k.
Mike Buess
Origin WebRing Member |
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segovi01
Mexico
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Posted - 10/23/2006 : 12:14:48 PM
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dear sir:
yes, you are right,thank you for your help and pacience
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A problem of a sigmoidal shape