Re: [R] Fitting data from a spectrophotometer.

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From: Gabor Grothendieck (ggrothendieck@myway.com)
Date: Thu 13 May 2004 - 09:52:46 EST


Message-id: <loom.20040513T014106-923@post.gmane.org>


Perhaps you really prefer something with a continuous first derivative?
In that case, all the continuous cumulative distribution functions have
a sigmoidal shape and might be suitable. You could fit pnorm, plogis or tanh
with suitable scaling and location parameters using nls. An example
of fitting a logistic is at

https://stat.ethz.ch/pipermail/r-help/2004-April/048385.html

TAPO (Thomas Agersten Poulsen <tapo <at> novozymes.com> writes:

:
: Dear R-list,
:
: It is not uncommon for laboratory equipment (e.g. spectrophotometers)
to have a linear response in a
: certain interval and then go into saturation. I wonder if there is an R-
function that models this; for
: instance by estimating the breakpoint and fitting a line below the
breakpoint and a constant above.
:
: Best regards
: Thomas Poulsen

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