[R] Select rows with distinct values in a column and other conditions

[Joshua Wiley]

Dear Sarah,

What you will need is a series of logical conditions.  ?Logic or ?"|"
should pull up the documentation on the logical operators available to
use.   Because this list does not accept HTML emails (see the posting
guide), your data frame did not come through in any coherent form.
Can you resend the data using the following procedure:

Suppose your data frame is named "dfrm" (but substitute its actual
name).  At the R console, type:

dput(dfrm)

this will output how R "sees" the data to the console, then copy and
paste that whole jumble of text from R to your email and send it to
us.  This is one of the easiest way for us to read in small amounts of
data, and it should be easy for you to provide too.

Cheers,

Josh

On Mon, Jan 31, 2011 at 6:22 AM, sarah bauduin <sarahbauduin at hotmail.fr> wrote:
>
> My data frame looks like:
>   SightingID PA1 PA2 PlotID InOverlap Area1        2001   1 -99    392         Y        0.22        2002   1 -99    388         Y        0.253        2008   1  NA    104         N        0.344        2010   1  NA     71         N        0.185        2012   1  NA     61         N         0.166        2013   1  NA     61         N         0.227        2014   1  NA     62         N          0.258        2015   1  NA     63         N         0.199        2016   1  NA     63         N          0.310       2017   1  NA     63         N         0.2511       2018   1  NA     63         N        0.2612       2019   1  NA     63         N         0.2613       2020   1  NA     64         N         0.33  14       2021   1  NA     64         N         0.4215       2022   1  NA     85         N         0.0816       2023   0   1     95         Y           0.11 17       2024   1  NA     93         N         0.2318       2025   1  NA    106         N         0.419       2026   1  NA    134 !
>         N        0.28
> The only unique values in the data frame are the SightingID. I would like to obtain a new data frame with unique PlotID values based on several conditions:- return the row if there is only one SightingID for the PlotID- if there is several SightingID for the same PlotID value:     -select first the SightingID for which PA1=0,      if there is several SightingID with PA1=0 for the same PlotID select the one with the highest value in Area,     if there is several SightingID with PA1=0 for the same PlotID with the highest value for Area select one SightingID at random     - select the SightingID for which PA1 is not equal to 0 based on the highest value in Area (and at random if there are several with the highest value in Area)
> I have no idea how to do that, can someone help me please ?     Sarah
>        [[alternative HTML version deleted]]
>
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/