# Re: [R] Simple indexing conundrum

From: Jim Brennan <jfbrennan_at_rogers.com>
Date: Fri 01 Jul 2005 - 22:45:04 EST

> 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@stat.math.ethz.ch
[mailto:r-help-bounces@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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