Onion growth data
Description
The Ratkowsky3
data frame has 15 rows and 2 columns.
Format
This data frame contains the following columns:
 y

A numeric vector of dry weights of onion bulbs and tops.
 x

A numeric vector of growing times.
Details
This model and data are an example of fitting sigmoidal growth curves taken from Ratkowsky (1983). The response variable is the dry weight of onion bulbs and tops, and the predictor variable is growing time.
Source
Ratkowsky, D.A. (1983). Nonlinear Regression Modeling. New York, NY: Marcel Dekker, pp. 62 and 88.
Examples
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  Try < function(expr) if (!inherits(val < try(expr), "tryerror")) val
plot(y ~ x, data = Ratkowsky3)
## causes NA/NaN/Inf error
Try(fm1 < nls(y ~ b1 / ((1+exp(b2b3*x))**(1/b4)), data = Ratkowsky3,
start = c(b1 = 100, b2 = 10, b3 = 1, b4 = 1),
trace = TRUE))
Try(fm1a < nls(y ~ b1 / ((1+exp(b2b3*x))**(1/b4)), data = Ratkowsky3,
start = c(b1 = 100, b2 = 10, b3 = 1, b4 = 1),
alg = "port", trace = TRUE))
Try(fm2 < nls(y ~ b1 / ((1+exp(b2b3*x))**(1/b4)), data = Ratkowsky3,
start = c(b1 = 700, b2 = 5, b3 = 0.75, b4 = 1.3),
trace = TRUE))
Try(fm2a < nls(y ~ b1 / ((1+exp(b2b3*x))**(1/b4)), data = Ratkowsky3,
start = c(b1 = 700, b2 = 5, b3 = 0.75, b4 = 1.3),
alg = "port", trace = TRUE))
Try(fm3 < nls(y ~ 1 / ((1+exp(b2b3*x))**(1/b4)), data = Ratkowsky3,
start = c(b2 = 10, b3 = 1, b4 = 1), algorithm = "plinear",
trace = TRUE))
Try(fm4 < nls(y ~ 1 / ((1+exp(b2b3*x))**(1/b4)), data = Ratkowsky3,
start = c(b2 = 5, b3 = 0.75, b4 = 1.3), algorithm = "plinear",
trace = TRUE))

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