Hey R list,
A beginners question. How can I do the following:
In my research population it is possible that several items can appear
several times, measured on different moments in time. This is being supplied
in a total list with all observations identified by a number (per item) and
a moment of observation (date). Now I want to make a unique list of this
observation preserving the characteristics of the first observation. As
example:
Tree disease date
Tree1 leaves 01-01-2009
Tree2 roots 13-09-2009
Tree1 roots 24-10-2009
Now I want to create a list of unique elements (in the example only once
Tree1 and Tree2) with the first observed disease and date. For the example
the result would look like:
Tree disease date
Tree1 roots 24-10-2008
Tree2 roots 13-09-2009
Can someone help me with this question?
Thanks in advance.
Kind regards,
John
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