Displaying 5 results from an estimated 5 matches for "conditiion".
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2023 Nov 06
2
non-linear regression and root finding
Thanks a lot! This was amazing. I'm not sure I see how the conditiion
pK1 < pK2 < pK3 is enforced? - it comes from the derivation via
generalized Henderson-Hasselbalch but perhaps it is not really
necessary. Anyway, the use of Vectorize did the trick!
Best wishes
Troels
Den 06-11-2023 kl. 19:19 skrev Ivan Krylov:
> ? Mon, 6 Nov 2023 17:53:49 +0100
>...
2023 Nov 07
1
non-linear regression and root finding
G'day Troels,
On Mon, 6 Nov 2023 20:43:10 +0100
Troels Ring <tring at gvdnet.dk> wrote:
> Thanks a lot! This was amazing. I'm not sure I see how the conditiion
> pK1 < pK2 < pK3 is enforced?
One way of enforcing such constraints (well, in finite computer
arithemtic only "<=" can be enforced) is to rewrite the parameters as:
pK1 = exp(theta1) ## only if pK1 > 0
pK2 = pK1 + exp(theta2)
pK3 = pk2 + exp(theta3)
And then use...
2023 Nov 07
1
non-linear regression and root finding
...h case we have pK1 = -exp(theta1)?
Best wishes
Troels
Den 07-11-2023 kl. 05:10 skrev Berwin A Turlach:
> G'day Troels,
>
> On Mon, 6 Nov 2023 20:43:10 +0100
> Troels Ring <tring at gvdnet.dk> wrote:
>
>> Thanks a lot! This was amazing. I'm not sure I see how the conditiion
>> pK1 < pK2 < pK3 is enforced?
> One way of enforcing such constraints (well, in finite computer
> arithemtic only "<=" can be enforced) is to rewrite the parameters as:
>
> pK1 = exp(theta1) ## only if pK1 > 0
> pK2 = pK1 + exp(theta2)
> pK3 = p...
2023 Nov 06
1
non-linear regression and root finding
...uot;delta" parameters from below.
Note that nls() can only handle bounds in the "port" algorithm, and the
man page rather pours cold water on using that algorithm.
Best, JN
On 2023-11-06 14:43, Troels Ring wrote:
> Thanks a lot! This was amazing. I'm not sure I see how the conditiion pK1 < pK2 < pK3 is enforced? - it comes from the
> derivation via generalized Henderson-Hasselbalch but perhaps it is not really necessary. Anyway, the use of Vectorize
> did the trick!
>
> Best wishes
> Troels
>
> Den 06-11-2023 kl. 19:19 skrev Ivan Krylov:
>>...
2023 Nov 06
1
non-linear regression and root finding
? Mon, 6 Nov 2023 17:53:49 +0100
Troels Ring <tring at gvdnet.dk> ?????:
> Hence I wonder if I could somehow have non linear regression to find
> the 3 pK values. Below is HEPESFUNC which delivers charge in the
> fluid for known pKs, HEPTOT and SID. Is it possible to have
> root-finding in the formula with nls?
Sure. Just reformulate the problem in terms of a function that