[R] Cleaning database: grep()? apply()?
Jonas Malmros
jonas.malmros at gmail.com
Tue Nov 13 20:34:04 CET 2007
Dear R users,
I have a huge database and I need to adjust it somewhat.
Here is a very little cut out from database:
CODE NAME DATE DATA1
4813 ADVANCED TELECOM 1987 0.013
3845 ADVANCED THERAPEUTIC SYS LTD 1987 10.1
3845 ADVANCED THERAPEUTIC SYS LTD 1989 2.463
3845 ADVANCED THERAPEUTIC SYS LTD 1988 1.563
2836 ADVANCED TISSUE SCI -CL A 1987 0.847
2836 ADVANCED TISSUE SCI -CL A 1989 0.872
2836 ADVANCED TISSUE SCI -CL A 1988 0.529
What I need is:
1) Delete all cases containing -CL A (and also -OLD, -ADS, etc) at the end
2) Delete all cases that have less than 3 years of data
3) For each remaining case compute ratio DATA1(1989) / DATA1(1987)
[and then ratios involving other data variables] and output this into
new database consisting of CODE, NAME, RATIOs.
Maybe someone can suggest an effective way to do these things? I
imagine the first one would involve grep(), and 2 and 3 would involve
apply family of functions, but I cannot get my mind around the actual
code to perform this adjustments. I am new to R, I do write code but
usually it consists of for-functions and plotting. I would much
appreciate your help.
Thank you in advance!
--
Jonas Malmros
Stockholm University
Stockholm, Sweden
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