# Ratkowsky3: Onion growth data In NISTnls: Nonlinear least squares examples from NIST

## 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), "try-error")) val plot(y ~ x, data = Ratkowsky3) ## causes NA/NaN/Inf error Try(fm1 <- nls(y ~ b1 / ((1+exp(b2-b3*x))**(1/b4)), data = Ratkowsky3, start = c(b1 = 100, b2 = 10, b3 = 1, b4 = 1), trace = TRUE)) Try(fm1a <- nls(y ~ b1 / ((1+exp(b2-b3*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(b2-b3*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(b2-b3*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(b2-b3*x))**(1/b4)), data = Ratkowsky3, start = c(b2 = 10, b3 = 1, b4 = 1), algorithm = "plinear", trace = TRUE)) Try(fm4 <- nls(y ~ 1 / ((1+exp(b2-b3*x))**(1/b4)), data = Ratkowsky3, start = c(b2 = 5, b3 = 0.75, b4 = 1.3), algorithm = "plinear", trace = TRUE)) ```

NISTnls documentation built on May 29, 2017, 3:49 p.m.