[R] Info
Andrea Calandra
a.CALANDRA at mclink.it
Thu Jul 17 15:21:05 CEST 2003
Sorry
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.
i try:
yeld.fit <- nls( y ~ a + (c.-a)/(1+exp(-b*(x-m))),
data = yeld,
start = list( a= 0, c.=2, b= 1, m=4 ),
trace = TRUE )
where yeld is a data.frame
x y
1 1 1
2 2 2
3 3 3
4 4 4
5 5 5
but give me an error: << exceeded number of itwerations>>
thank you
Andrea
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