Dear Contributors
thanks for any help you can provide. I searched the threads
but I could not find any query that satisfied my needs.
This is my database:
index time values
13732 27965 DATA.Q211.SUM.Index 04/08/11 1.42
13733 27974 DATA.Q211.SUM.Index 05/10/11 1.45
13734 27984 DATA.Q211.SUM.Index 06/01/11 1.22
13746 28615 DATA.Q211.TDS.Index 04/07/11 1.35
13747 28624 DATA.Q211.TDS.Index 05/20/11 1.40
13754 29262 DATA.Q211.UBS.Index 05/02/11 1.30
13755 29272 DATA.Q211.UBS.Index 05/03/11 1.48
13761 29915 DATA.Q211.UCM.Index 04/28/11 1.43
13768 30565 DATA.Q211.VDE.Index 05/02/11 1.48
13775 31215 DATA.Q211.WF.Index 04/14/11 1.44
13776 31225 DATA.Q211.WF.Index 05/12/11 1.42
13789 31865 DATA.Q211.WPC.Index 04/01/11 1.40
13790 31875 DATA.Q211.WPC.Index 04/08/11 1.42
13791 31883 DATA.Q211.WPC.Index 05/10/11 1.43
13804 32515 DATA.Q211.XTB.Index 04/29/11 1.50
13805 32525 DATA.Q211.XTB.Index 05/30/11 1.40
13806 32532 DATA.Q211.XTB.Index 06/28/11 1.43
I need to select only the rows of this database that correspond to each
of the first occurrences of the string represented in column
index. In the example shown I would like to obtain a new
data.frame which is
index time values
13732 27965 DATA.Q211.SUM.Index 04/08/11 1.42
13746 28615 DATA.Q211.TDS.Index 04/07/11 1.35
13754 29262 DATA.Q211.UBS.Index 05/02/11 1.30
13761 29915 DATA.Q211.UCM.Index 04/28/11 1.43
13768 30565 DATA.Q211.VDE.Index 05/02/11 1.48
13775 31215 DATA.Q211.WF.Index 04/14/11 1.44
13789 31865 DATA.Q211.WPC.Index 04/01/11 1.40
13804 32515 DATA.Q211.XTB.Index 04/29/11 1.50
As you can see, it is not the whole string to change,
rather a substring that is part of it. I want to select
only the first values related to the row that presents for the first time
the different part of the string(substring).
I know how to select rows according to a substring condition on the
index column, but I cannot use it here because the substring changes
and moreover the number of occurrences per substring is variable.
Thank you for any help you can provide.
Francesca
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