[R] deleting rows containing a letter

[David Winsemius]

On May 11, 2011, at 10:01 AM, David Winsemius wrote:

>
> On May 11, 2011, at 7:55 AM, chris20 wrote:
>
>> Hi
>> I have dataframe with different plot numbers in and different  
>> subplots as
>> letters at the end of the plot number i.e. 1a, 1b 2-1a etc.
>> I want to delete all rows that end in a specific letter eg...
>>
>> treat<-c("1a","1b","1c","2a","2b","2c","2-1a","2-1b","2-1c")
>> a1<-1:9
>> b1<-9:1
>> d1<-data.frame(treat,a1,b1)
>>
> > d1[-grep("c$", d1$treat), ]
>  treat a1 b1
> 1    1a  1  9
> 2    1b  2  8
> 4    2a  4  6
> 5    2b  5  5
> 7  2-1a  7  3
> 8  2-1b  8  2
>
>> How do I remove all rows where treat ends in "c" ?  I have tried  
>> the usual
>> ways of deleting rows but nothing works.
>
> Not sure what the usual ways are for you but negative indexing is  
> the usual way for me.
>
> (Could also use subset, I suppose)

As here with grepl rather than grep:

 > subset(d1, !grepl("c$", d1$treat))
   treat a1 b1
1    1a  1  9
2    1b  2  8
4    2a  4  6
5    2b  5  5
7  2-1a  7  3
8  2-1b  8  2

In case you are new to grepping, the $ indicates the end of a string  
and therefore 'c' will match any 'c' at the end of the string. grepl  
creates a logical vector that flags matches and non-matches and the  
'!' operator logically inverts it.



David Winsemius, MD
West Hartford, CT