exp1 {nlrwr}R Documentation

Nitrogen content over time

Description

The two datasets contain measurements of nitrogen over 16.5 years from two experiments involving different ways of adding residues to soil. Data have been summarised each year into average response, empirical standard deviation and number of replicates.

Usage

data(exp1)

Format

A data frame with 8 observations on the following 4 variables.

time
a numeric vector of years since start of the experiments
Nremaining
a numeric vector of nitrogen content (in percent)
stdev
a numeric vector containing standard deviations
norep
a numeric vector containing the number of replicates

Details

The appropriate model for these datasets is the bi-exponential model.

Source

Data are kindly provided by Guillaume Laberge, Department of Agricultural Sciences, Faculty of Life Sciences, University of Copenhagen.

References

Laberge, G., Ambus, P., Hauggaard-Nielsen, H., Jensen, E. S. (2006) Stabilization and plant uptake of N from 15N-labelled pea residue 16.5 years after incorporation in soil, Soil Biology & Biochemistry, 38, 1998-2000.

Examples


## Fitting models with and without weights
exp1.m1<-nls(Nremaining~SSbiexp(time, a1,a2,b1,b2),data=exp1)
exp1.m2<-nls(Nremaining~SSbiexp(time, a1,a2,b1,b2),data=exp1, weights=norep/(stdev^2))

exp2.m1<-nls(Nremaining~SSbiexp(time, a1,a2,b1,b2),data=exp2)
exp2.m2<-nls(Nremaining~SSbiexp(time, a1,a2,b1,b2),data=exp2, weights=norep/(stdev^2))

## Summary output
summary(exp1.m1)
summary(exp1.m2)

summary(exp2.m1)
summary(exp2.m2)


[Package nlrwr version 1.0-6 Index]