p12.12 {MPV}

Data Set for Problem 12-12

Description

The p12.12 data frame has 18 observations on an chemical experiment. A nonlinear model relating concentration to reaction time and temperature with an additive error is proposed to fit these data.

Usage

data(p12.12)

Format

This data frame contains the following columns:

x1

reaction time (in minutes)

x2

temperature (in degrees Celsius)

y

concentration (in grams/liter)

Source

Montgomery, D.C., Peck, E.A., and Vining, C.G. (2001) Introduction to Linear Regression Analysis. 3rd Edition, John Wiley and Sons.

Examples

data(p12.12)
attach(p12.12)
# fitting the linearized model 
logy.lm <- lm(I(log(y))~I(log(x1))+I(log(x2)))
summary(logy.lm)
plot(logy.lm, which=1)  # checking the residuals
# fitting the nonlinear model
y.nls <- nls(y ~ theta1*I(x1^theta2)*I(x2^theta3), start=list(theta1=.95, 
theta2=.76, theta3=.21))
 summary(y.nls)
 plot(resid(y.nls)~fitted(y.nls)) # checking the residuals