bootstrapping lambda values from projections matrices

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bootstrapping lambda values from projections matrices

Saskia Sandring
Dear all,

I'm working with a population projections matrix model from demographic
data. The dominant eigenvalue of the matrix is the growth rate of the
population (lambda). I would like to estimate confidence intervals for the
lambda values with bootstrap.
The function for calculating the eigenvalue I wrote like this: <- function(d,i){
    sum(d$classyear1[i]==1&d$classyear2[i]==3)/sum(d$classyear1[i]==1), 0,


Now, in the pooled matrix from all years I would like to sample in a way
that the number of bootstrap samples taken from each year is equal to the
number of data points from each year. Therefore I'm defining strata=year.

boot1 <- boot(myfile,, 5000, strata=myfile$year); boot1

Is this the correct way to do it or did I misunderstand the
strata-argument? I checked in Davison, A.C. and Hinkley, D.V. (1997), but
I'm still not quite sure.

Thanks very much in advance for your help!

Saskia Sandring

Saskia Sandring

Avd. för växtekologi, Evolutionsbiologiskt centrum, Uppsala universitet
Dept. of Plant Ecology, Evolutionary Biology Centre, Uppsala University
Villavägen 14 tel: 018-471 2870 (int +46 18 4712870)
SE-752 36 Uppsala fax: 018-55 34 19 (int +46 18 553419)
SWEDEN email: [hidden email]

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