Hello, If I have a database of the form: ID RN TN OBS 1 1 1 3.2 1 1 2 3.1 1 1 3 4.0 1 1 4 3.9 1 2 1 3.6 1 2 2 3.9 1 2 3 4.2 1 4 1 3.5 1 4 2 4.4 1 4 3 4.1 2 2 1 5.2 2 2 2 4.8 2 2 3 4.9 3 1 1 5.1 3 1 2 5.0 3 1 3 5.0 3 1 4 5.2 3 2 1 5.6 3 2 2 5.3 3 2 3 5.3 3 2 4 4.9 3 2 5 5.1 3 3 1 5.9 3 3 2 5.9 3 3 3 5.8 (ID = identifier, RN = control rank, TN = test number within the control and OBS = Observation) If the control row vary from 1 to 4 (in my original database with over 800 miles observations)), how do I keep only individuals with successive control row as 1; 1 and 2; 1, 2 and 3; Or 1, 2, 3 and 4. If for example an individual has two non-successive control 1 and 3 , because he has missed control 2, it will only be shown in the database by control 1. This means that if an individual misses a control, the next row of conctrol will no longer be considered in the database. The result of my example is as follows: ID RN TN OBS 1 1 1 3.2 1 1 2 3.1 1 1 3 4.0 1 1 4 3.9 1 2 1 3.6 1 2 2 3.9 1 2 3 4.2 3 1 1 5.1 3 1 2 5.0 3 1 3 5.0 3 1 4 5.2 3 2 1 5.6 3 2 2 5.3 3 2 3 5.3 3 2 4 4.9 3 2 5 5.1 3 3 1 5.9 3 3 2 5.9 3 3 3 5.8 thank you for helping me.
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