
I only have a few values in my example, but the real data set might have 
20-100 rows with A="X".  So how do I pick just the three highest ones?

-N


On 8/26/09 2:46 AM, Ottorino-Luca Pantani wrote:
> df.mydata[df.mydata$A=="X" AND df.mydata$C < 2, ]
> will do the job ?
>
> 8rino
>
> Noah Silverman ha scritto:
>> Hi,
>>
>> I'm trying to find an easy way to do this.
>>
>> I want to select the top three values of a specific column in a 
>> subset of rows in a data.frame.  I'll demonstrate.
>>
>> A    B    C
>> x    2    1
>> x    4    1
>> x    3    2
>> y    1    5
>> y    2    6
>> y    3    8
>>
>>
>> I want the top 3 values of B from the data.frame where A=X and C <2
>>
>> I could extract all the rows where C<2, then sort by B, then take the 
>> first 3.  But that seems like the wrong way around, and it also will 
>> get messy with real data of over 100 columns.
>>
>> Any suggestions?
>>

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