I have been using nlsr() to fit s curves to Covid-19 data over the past few
weeks and I have not had any issues.
Bernard
Sent from my iPhone so please excuse the spelling!"
> On May 13, 2020, at 5:16 PM, Abby Spurdle wrote:
>
> Hi Christofer,
>
> This doesn't really answer your question.
> B
> It's possible that Martin's package, cobs, can do this, but not sure,
> I haven't tried it.
> And there may be other R packages for fitting splines/smoothers to
> data, subject to shape constraints.
Further to my previous post.
I read through the documentation for the cobs package.
And (someone
Hi Christofer,
This doesn't really answer your question.
But if the goal is to fit an S-shaped curve to data, with increased
flexibility...
(I'm assuming that's the goal).
...then I'd like to note the option of splines (or smoothing), subject
to shape constraints...
My guess, is it's probably ea
Many moons ago (I think early 80s) I looked at some of the global optimizers,
including several based on intervals. For problems of this size, your suggestion
makes a lot of sense, though it has been so long since I looked at those
techniques
that I will avoid detailed comment.
I've not looked to
Also, in the full curve referenced on Wikpedia, the parameters Q And M are
confounded - you only need one or the other But not both. If you are using both
and trying to estimate them both you will have problems.
I have fitted these curves quite easily using the Solver in Excel.
Bernard
Sent fro
John, have you ever looked at interval optimization as an alternative since it
can lead to provably global minima?
Bernard
Sent from my iPhone so please excuse the spelling!"
> On May 13, 2020, at 8:42 AM, J C Nash wrote:
>
> The Richards' curve is analytic, so nlsr::nlxb() should work better
The Richards' curve is analytic, so nlsr::nlxb() should work better than nls()
for getting derivatives --
the dreaded "singular gradient" error will likely stop nls(). Also likely,
since even a 3-parameter
logistic can suffer from it (my long-standing Hobbs weed infestation problem
below), is
th
Shouldn't be hard to set up with nls(). (I kind of suspect that the Richards
curve has more flexibility than data can resolve, especially the subset
(Q,B,nu) seems highly related, but hey, it's your data...)
-pd
> On 13 May 2020, at 11:26 , Christofer Bogaso
> wrote:
>
> Hi,
>
> Is there a
Hi Christofer
Try FlexParamCurve or maybe drc package.
Cheers
Petr
> -Original Message-
> From: R-help On Behalf Of Christofer Bogaso
> Sent: Wednesday, May 13, 2020 11:26 AM
> To: r-help
> Subject: [R] Fitting Richards' curve
>
> Hi,
>
> Is the
Hi,
Is there any R package to fit Richards' curve in the form of
https://en.wikipedia.org/wiki/Generalised_logistic_function
I found there is one package grofit, but currently defunct.
Any pointer appreciated.
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