Replacing repeated values with Missing i.e "."

[Fatimah Shah]

Hello,
I am working on a data set where I am stucked with something. So basically, I have a panel data where can be same age in two subsequent year (because of the survey design this is possible). Now I want to replace the second observation with a dot "." otherwise I will lose some important information. For instance in following sample data set, respondent no 102 is year 2003 and 2004 and I have two different education levels for this particular age and now I want to replace second value (in this case) it is grade 7 with a dot. But whatever I am trying is giving me different result. Can anyone please help me with this?

Individual No	Year	Age	Education Level
101	2002	10	grade 5
101	2003	10	grade 6
102	2001	9	grade 4
102	2002	10	grade 5
102	2003	11	grade 6
102	2004	11	grade 7
103	2003	9	grade 4
103	2004	9	grade 5
103	2005	11	grade 7
104	2005	10	grade 5
105	2002	8	grade 3
105	2003	9	grade 4
105	2004	10	grade 5
105	2005	10	grade 6
105	2006	12	grade 7
106	2005	10	grade 5
107	2003	11	grade 6
107	2004	11	grade 7
107	2005	13	grade 8
107	2006	14	grade 9
107	2007	15	grade 10
108	2006	9	grade 4
108	2007	10	grade 5
108	2008	10	grade 6
109	2002	8	grade 3
109	2003	9	grade 4
109	2004	9	grade 5
109	2005	11	grade 6
110	2002	10	grade 5
110	2003	11	grade 6
110	2004	11	grade 7

[Nick Cox]

I don't get how replacing values with missing is avoiding a loss of information. It is increasing the loss of information.

[Fatimah Shah]

I will have information in other variables for that particular year that are useful for other parts of my research so I cannot completely delete that individual.

[Nick Cox]

Sure, but why mangle your data?