Noah Silverman a écrit :
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
Hi,
and now?
df.mydata$B[order(df.mydata[df.mydata$A=="X" AND df.mydata$C < 2,
]$B)][length(df.mydata$B)-3:length(df.mydata$B)]
cheers,
ML
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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