Hello.  I am fitting a repeated measures model using the mixed model
function of R (lme).  However, the hierarchical structure is
complicated.  Each individual sheep is measured a number of times (once
per year) over its life (ranging from once to 12 consecutive years).
However, this longitudinal study involves many different cohorts and so
many different individuals (of different ages) are measured each year.
Therefore, individuals measured in the same year are not independent.  A
typical data set might look like this:

Ind   age   year  mass

1     1     1984  2.3

1     2     1985  4.3

1     3     1986  5.5

...

2     1     1985  3.3

2     2     1986  4.1

...

 

Can someone explain how to specify this in the random part of the model
specification in the lme function of R?  If I were to ignore the "year"
effect, I would specify: lme(mass~age, random=age|ind)

 

 

Bill Shipley

Associate Editor, Ecology

North American Editor, Annals of Botany

Département de biologie, Université de Sherbrooke,

Sherbrooke (Québec) J1K 2R1 CANADA

Bill.Shipley@USherbrooke.ca

 <http://callisto.si.usherb.ca:8080/bshipley/>
http://callisto.si.usherb.ca:8080/bshipley/

 


	[[alternative HTML version deleted]]


