[R] Re: Info

Douglas Bates bates at stat.wisc.edu
Wed Jul 16 14:42:15 CEST 2003

```Andrea Calandra <a.CALANDRA at mclink.it> writes:

> I'm student in biomedical engineer and i have to solve this formula
> for immuno-assay. I need to design a calibration curve
>
> But i don't understand How can i write this formula in R language:
> 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
>
> I have to calculate the parameters (a,b,c,m).After with X that i know
> i calculate the Y.

You have asked essentially the same question three or four times and
have gotten the same answer each time.  You tell us IN ALL CAPS that
you are doing five-point interpolation and we point out that you have
only four parameters in that formula.  Asking the same question over
and over and over again will not change that.  Perhaps you should
accept the fact that you cannot interpolate five points with a
four-parameter model then reconsider your question.

If you wish to do a least-squares fit of those parameters you can use
nls and SSfpl as I suggested in an earlier response.

```