# Ratkowsky2_opt: Pasture yield data In NISTopt: Nonlinear least squares examples from NIST in form of functions for optim() and optimx()

## 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

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21``` ```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) ```

NISTopt documentation built on July 25, 2017, 3:01 p.m.