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 Iteration with 3 unknown paramters		  New Topic  Reply to Topic
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Menten

Germany
2 Posts
Posted - 05/13/2022 :  08:26:23 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hello guys,

I have a degradation over time and need a iteration with 3 unknown parameters.



My formula is t=(c(0) - c(t) - km * (ln (c(t)/c(0)) ) / vmax

The time "t" is my dependent variable and I although know c(0)=3335.

time CSB
0 - 242
0 - 3335
1 - 1977
2 - 2641
3 - 2297
4 - 1965
5 - 1637
6 - 1315
7 - 919
9 - 290
24 - 89

How can I get km, c(t) and vmax with a nonlinear regression ?

Thanks a lot!

YimingChen

1592 Posts
Posted - 05/13/2022 :  09:01:04 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
You can use the simple fit app. Check the page below, it contains a Youtube link of the tutorial.
https://www.originlab.com/fileExchange/details.aspx?fid=239

James
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Menten

Germany
2 Posts
Posted - 05/16/2022 :  03:08:22 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thank you.

I used the simple fit, but still can't get the right fit.

I tipped in my formula as y=(x0 -x -km * (ln(x/x0))) / vmax and fixed x0.

But the fix didn't work, because of mutual dependency exists between parameters. (Error -203)
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