[R] Simple indexing conundrum

From: Martin Henry H. Stevens <HStevens_at_MUOhio.edu>
Date: Fri 01 Jul 2005 - 21:54:54 EST


My apologies in advance for my thickness but I can't seem to solve the following, seemingly simple, data manipulation problem:

I have a data frame that contains multiple factors and multiple continuous response variables, but duplicates of some factor combinations. The duplicates contain bad data, so I would like to eliminate the duplicates. I would like to retain the entire rows identified by the maximum value of one particular continuous response variable.

For instance,

 >data(airquality)

 > str(airquality)
`data.frame': 153 obs. of 6 variables:
$ Ozone : int 41 36 12 18 NA 28 23 19 8 NA ...
$ Solar.R: int 190 118 149 313 NA NA 299 99 19 194 ...
$ Wind : num 7.4 8 12.6 11.5 14.3 14.9 8.6 13.8 20.1 8.6 ...
$ Temp : int 67 72 74 62 56 66 65 59 61 69 ...
$ Month : int 5 5 5 5 5 5 5 5 5 5 ...
$ Day : int 1 2 3 4 5 6 7 8 9 10 ...

I would like to subset airquality, retaining only the rows, containing the maximum Solar.R for each month.

Any solution would be greatly appreciated.

Regards,
Hank

Dr. Martin Henry H. Stevens, Assistant Professor 338 Pearson Hall
Botany Department
Miami University
Oxford, OH 45056

Office: (513) 529-4206
Lab: (513) 529-4262
FAX: (513) 529-4243

http://www.cas.muohio.edu/botany/bot/henry.html
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http://www.muohio.edu/botany/

"E Pluribus Unum"

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