[R] extract data features from subsets

[Williams Scott]

I have a large dataset similar to this:

ID	time	result
A	1	5
A	2	2
A	3	1
A	4	1
A	5	1
A	6	2
A	7	3
A	8	4
B	1	3
B	2	2
B	3	4
B	4	6
B	5	8

I need to extract a number of features for each individual in it (identified by "ID"). These are:
* The lowest result (the nadir)
* The time of the nadir - but if the nadir level is present at >1 time point, I need the minimum and maximum time of nadir
* For the time period from maximum time of nadir to the last result, I need the coefficient from a lm(result~time) 

The result would be a table looking like:

ID	NadirLevel	NadirFirstTime	NadirLastTime 	Slope	
A	1		3			5			1
B	2		2			2			2

I can manage to extract all the required elements in a very cumbersome loop, but I am sure an elegant method using apply() or the like could be devised but I cant presently understand the necessary syntax. An suggestions appreciated.

Thanks 
Scott
_____________________________
 
Dr. Scott Williams
Peter MacCallum Cancer Centre
Melbourne, Australia
ph +61 3 9656 1111
fax +61 3 9656 1424
scott.williams at petermac.org 
 


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