Ratkowsky2 {NISTnls} | R Documentation |
Pasture yield data
Description
The Ratkowsky2
data frame has 9 rows and 2 columns.
Format
This data frame contains the following columns:
- y
-
A numeric vector of pasture yields.
- 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 pasture yield, and the predictor variable is growing time.
Source
Ratkowsky, D.A. (1983). Nonlinear Regression Modeling. New York, NY: Marcel Dekker, pp. 61 and 88.
Examples
Try <- function(expr) if (!inherits(val <- try(expr), "try-error")) val
plot(y ~ x, data = Ratkowsky2)
Try(fm1 <- nls(y ~ b1 / (1+exp(b2-b3*x)), data = Ratkowsky2, trace = TRUE,
start = c(b1 = 100, b2 = 1, b3 = 0.1)))
Try(fm1a <- nls(y ~ b1 / (1+exp(b2-b3*x)), data = Ratkowsky2,
trace = TRUE, alg = "port",
start = c(b1 = 100, b2 = 1, b3 = 0.1)))
Try(fm2 <- nls(y ~ b1 / (1+exp(b2-b3*x)), data = Ratkowsky2, trace = TRUE,
start = c(b1 = 75, b2 = 2.5, b3 = 0.07)))
Try(fm2a <- nls(y ~ b1 / (1+exp(b2-b3*x)), data = Ratkowsky2,
trace = TRUE, alg = "port",
start = c(b1 = 75, b2 = 2.5, b3 = 0.07)))
Try(fm3 <- nls(y ~ 1 / (1+exp(b2-b3*x)), data = Ratkowsky2, trace = TRUE,
start = c(b2 = 1, b3 = 0.1), alg = "plinear"))
Try(fm4 <- nls(y ~ 1 / (1+exp(b2-b3*x)), data = Ratkowsky2, trace = TRUE,
start = c(b2 = 2.5, b3 = 0.07), alg = "plinear"))
## Using a self-starting model
Try(fm5 <- nls(y ~ SSlogis(x, Asym, xmid, scal), data = Ratkowsky2))
summary(fm5)
[Package NISTnls version 0.9-13 Index]