Re: [R] Removing row with smallest value, for a given factor

From: Peter Ehlers <ehlers_at_ucalgary.ca>
Date: Sat, 23 Apr 2011 10:30:14 -0700

On 2011-04-23 07:02, David Winsemius wrote:
>
> On Apr 23, 2011, at 9:05 AM, - - wrote:
>
>> I have a table.
>> First column is a date, second column is an index and other columns
>> contains some other values.
>> I want to remove, for each date, the row with the smallest index (it
>> is not necessarily 1).
>>
>> ex: in the following table, I want to remove row 1 (2013-05-12 with
>> index 2) and row 8 (2013-05-13 with index 1)
>>
>> day index values
>> 1 2013-05-12 2 xxxx
>> 2 2013-05-12 3 xxxx
>> 3 2013-05-12 4 xxxx
>> 4 2013-05-12 5 xxxx
>> 5 2013-05-12 6 xxxx
>> 6 2013-05-12 7 xxxx
>> 7 2013-05-12 8 xxxx
>> 8 2013-05-13 1 xxxx
>> 9 2013-05-13 3 xxxx
>> 10 2013-05-13 4 xxxx
>> 11 2013-05-13 5 xxxx
>> 12 2013-05-13 6 xxxx
>> 13 2013-05-13 7 xxxx
>> 14 2013-05-13 8 xxxx
>> 15 2013-05-13 9 xxxx
>> 16 2013-05-13 10 xxxx
>> 17 2013-05-13 12 xxxx
>>
>
> Consider using ave and creating a logical vector that you then negate:
>
> > ave(dat$index, list(dat$day), FUN=function(x) x==min(x))
> [1] 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0
>
> dat[ -ave(dat$index, list(dat$day), FUN=function(x) x==min(x)), ]

ave() is one of those really handy functions, but I think that you meant

  dat[ !ave(dat$index, list(dat$day), FUN=function(x) x==min(x)), ]

Here's another way, using the plyr package

  require(plyr)
  ddply(dat, .(day), .fun = function(x) subset(x, index != min(index)))

Peter Ehlers

> --
>
> David Winsemius, MD
> West Hartford, CT
>
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Sat 23 Apr 2011 - 17:32:56 GMT

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