[R] info
Paul, David A
paulda at BATTELLE.ORG
Fri Jul 11 15:48:03 CEST 2003
The most commonly used dose-response functions for nonlinear calibration
curves are the four- and five-parameter logistic functions. The four-
parameter logistic is specified as
F(z) = delta + (alpha - delta)/(1 + (z/gamma)^beta)
so I'm not sure where you are getting your dose-response functional form
from. In any case, you can fit this model using either nls( ) or nlme( ),
depending on whether or not you want to fit a random-effects model.
For references related to the four- and five-parameter logistic functions,
you can read
1. Rodbard, D., and Frazier, G.R. (1975) "Statistical analysis of
radioligand
assay data," Methods Enzymol., vol. 37, p. 3 - 22.
2. Dudley, R.A., Edwards, P., and Ekins, R.P. (1985) "Guidelines for
immunoassay data processing," Clin. Chem., vol. 31, no. 8, p. 1264 - 1271
The first of these articles introduces the four-parameter logistic, and the
second refines its parametrization as well as introduces the five-parameter
logistic for use in situations where the calibration curve is asymmetric.
You should also acquire "Mixed Effects Models in S and Splus", by Drs.
Pinheiro and Bates if you intend to do anything with mixed effects models.
Best,
david paul
-----Original Message-----
From: Andrea Calandra [mailto:a.CALANDRA at mclink.it]
Sent: Thursday, July 10, 2003 11:39 AM
To: R-help at stat.math.ethz.ch
Subject: [R] info
HI
I'm a student in chemical engineering, and i have to implement an algoritm
about FIVE PARAMETERS INTERPOLATION for a calibration curve (dose, optical
density)
y = a + (c - a) /(1+ e[-b(x-m])
where
x = ln(analyte dose + 1)
y = the optical absorbance data
a = the curves top asymptote
b = the slope of the curve
c = the curves bottom asymptote
m = the curve X intercept
Have you never seen this formula, because i don't fine information or
lecterature about solution of this!!!
Can i help me
Hi
Mr. Calandra
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