[R] GEE - order of data?

[Anna Berthinussen]

Dear all,

I am trying to do a GEE on count data and I am having problems with  
how to order the data. Below is a simplified example of what my data  
looks like..

Route   Time     Day     Pass  Distance
1        30       1      4        0
1        60       1      12      200
1       120       1      25      600
1        30       2      8        0
1        60       2      17      200
1        120      2      32      600
2        30       1       0       0
2        60       1       4      200
2       120       1       11     600
2        30       2       3       0
2        60       2       42     200
2        120      2       3      600
etc...

My basic model: geeglm(Pass~Distance, id=Route, corstr="ar1")

Pass is the response variable (counts). I collected data along  
different routes (these represent the grouping structure, id=Route).  
As I walked each route I collected count data at different distances  
and times, therefore I need an AR-1 auto-correlation structure for the  
within route correlation. I gather that data must be organised within  
each block according to the time variable. However, I also completed  
each route on 2 separate nights, which makes ordering the data more  
complicated. Do I still just order the data within each block  
according to time (ignoring the fact that data were collected on  
different days), or do I need to somehow specifiy that the data were  
collected at different times on different days within each route? And  
how would this be done correctly?

I hope that makes sense. Any help would be much appreciated.

Thanks in advance,

Anna