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 NLCF-how to specify min &max of a param & stepsize		  New Topic  Reply to Topic
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fermiona

USA
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Posted - 08/25/2007 :  5:43:40 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Version (Select Help-->About Origin): 7.5
Operating System: XP

This is my first time to use Origin. I am trying to do a NLCF with 5 parameters. I have a range for each parameter and a step increment that I want the fitting program to use. I have no idea how to specify these in origin. To be more specific about my problem, lets say I have the function:

f(x)=x/p1+p2+p3+p4+p5

p1 should run from 0.1 to 0.9 and I want the step size to be 0.1
p2 should run from 0.1 to 0.2 and I want the step size to be 0.01

etc

Thanks in advance

Mike Buess

USA
3037 Posts
Posted - 08/26/2007 :  10:19:23 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
1> Your function has too many parameters. There are many (perhaps an infinite number) combinations of p2,p3,p4,p5 that will satisfy it. You must reduce the function to y = x/p1 + p2.

2> You can set the upper and lower bounds on the Parameter Constraints page (Options> Constraints) as shown below.

3> I don't think you can restrict the step size. The obvious 'linear' constraints rmod(p1,0.1)=0 and int(10*p1)=10*p1 do not work, perhaps because they are not really linear.



Mike Buess
Origin WebRing Member
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fermiona

USA
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Posted - 08/26/2007 :  12:57:55 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thank you. Unfortunately I cannot reduce the number of params (the actualy function is not like the one I posted.. it's very long and complicated). I figured how to specify the limits, but I've been strggling with finding a way to control the step size. Thanks for letting me know about the sw limitation.
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