[R] Fwd: How to conditionally remove dataframe rows?

[David Winsemius]

On Mar 6, 2013, at 3:21 PM, Francisco Carvalho Diniz wrote:

> Hi,
> 
> I have a data frame with two columns. I need to remove duplicated rows in
> first column, but I need to do it conditionally to values of the second
> column.
> 
> Example:
> 
>        Point_counts       Psi_Sp
> 
> 1            A                       0
> 2            A                       1
> 3            B                       1
> 4            B                       2
> 5            B                       0
> 6            C                       1
> 7            D                       1
> 8            D                       2
> 
> 
> I need to turn this data frame in one without duplicated rows at
> point-counts (one visit per point) but maintain the ones with maximum value
> at Psi_Sp, e.g. remove row 1 and maintain 2 or remove rows 3 and 5 and
> maintain 4. At the end I want a data frame like the one below:
> 
Try this:

dfrm <- dfrm[ order(dfrm[[1]], -dfrm[[2]] ) , ]  
#put desired rows at top of each Point_counts category

# then take top item in each category

dfrm[ !duplicated(dfrm[[1]]) , ] 

>         Point_counts           Psi_Sp
> 
> 1              A                           1
> 2              B                           2
> 3              C                           0
> 4              D                           2
> 
> How can I do it? I found several ways to edit data frames, but
> unfortunately I cound not use none of them.
> 
> I appreciate
> 
-- 

David Winsemius
Alameda, CA, USA