[R] Simple indexing conundrum

[Martin Henry H. Stevens]

Thank guys! Both solutions do what I need. Thanks.
Hank
On Jul 1, 2005, at 8:45 AM, Jim Brennan wrote:

> Here is a different approach I only send since the result is slightly
> different in that two rows are returned for Month 9 and the original 
> row
> number is retained.
>
>> max2<-function(x){max(x,na.rm=T)}
>> MonthMax<-ave(Solar.R,Month,FUN=max2)
>> new<-subset(airquality,Solar.R==MonthMax)
>> new<-subset(airquality,Solar.R==MonthMax)
>> new
>     Ozone Solar.R Wind Temp Month Day
> 16     14     334 11.5   64     5  16
> 45     NA     332 13.8   80     6  14
> 67     40     314 10.9   83     7   6
> 105    28     273 11.5   82     8  13
> 133    24     259  9.7   73     9  10
> 135    21     259 15.5   76     9  12
>
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Liaw, Andy
> Sent: July 1, 2005 8:31 AM
> To: 'Martin Henry H. Stevens'; R-Help
> Subject: Re: [R] Simple indexing conundrum
>
> Is this close to what you want?
>
>> air.sub <- do.call("rbind", lapply(split(airquality, 
>> airquality$Month),
> +                                    function(d) 
> d[which.max(d$Solar.R),]))
>> air.sub
>   Ozone Solar.R Wind Temp Month Day
> 5    14     334 11.5   64     5  16
> 6    NA     332 13.8   80     6  14
> 7    40     314 10.9   83     7   6
> 8    28     273 11.5   82     8  13
> 9    24     259  9.7   73     9  10
>
> Andy
>
>> From: Martin Henry H. Stevens
>>
>> 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
>> http://www.muohio.edu/ecology/
>> http://www.muohio.edu/botany/
>> "E Pluribus Unum"
>>
>> ______________________________________________
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>>
>>
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
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> PLEASE do read the posting guide!
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>
>
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
http://www.muohio.edu/ecology/
http://www.muohio.edu/botany/
"E Pluribus Unum"