R help - Jun 2008 - longitudinal data analysis

hie 



i am want to carryout a longitudinal analysis similar to the proc
catmod in SAS using The Weighted least squares method.my data is in the
following format.



Material   time1  time2    time3

1            

1

1

1

1

1

2

2

2

2

2

3

3

3

.

.

.

.

13



what i want to do is compare if there is a significant difference between the
materials.

and also if there is any sig difference between the times.

any help will be greatly apreciated

thanks






      
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