Fitting Richards' curve

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 easier to model the inverse of a growth
curve this way, than to model the growth curve directly.
In which case, a 4-piece to 10-piece spline should give considerably flexibly.

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.

If not, I'm guessing it wouldn't be too difficult to implement, via
extensions to the quadprog package, for quadratic programming.


On Wed, May 13, 2020 at 9:26 PM Christofer Bogaso

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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