[R] How to select partially (not completely) unique rows?

[Paul Hiemstra]

Hi Mark,

If you convert the data.frame to a Spatial class (see the sp-package 
documentation) you can use the function zerodist to find spatial 
locations that are at the same locations.

cheers,
Paul

Mark Na wrote:
> Dear R-helpers,
>
> I know how to use unique to select unique rows, e.g.
>
> unique.rows<-unique(dataframe)
>
> but I would like to select those rows that are unique only only TWO of my
> dataframe's columns (so, two rows with the same value on these two columns
> would not be kept, even if they had different values in other columns).
>
> For example, I have a dataframe with 10 columns, two of which are LATITUDE
> and LONGITUDE. I wish to keep only one row per unique combination of these
> two columns, so I've tried:
>
> unique.latlong<-extracted[unique(paste(extracted$latitude,extracted$longitude)),]
>
> but this is returning a dataframe of missing values (NAs).
>
> Could anyone point me in the right direction?
>
> Thanks! Mark Na
>
> 	[[alternative HTML version deleted]]
>
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-- 
Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
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