exp1 {nlrwr} | R Documentation |
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.
data(exp1)
A data frame with 8 observations on the following 4 variables.
time
Nremaining
stdev
norep
The appropriate model for these datasets is the bi-exponential model.
Data are kindly provided by Guillaume Laberge, Department of Agricultural Sciences, Faculty of Life Sciences, University of Copenhagen.
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.
## 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)