subset data frame based on percentage

i have a data frame that contains a data like this :

V1 V2 V3
1  2  0.34
1  3  0.31
1  4  0.12
1  5  0.12

the data frame is bigger but that's an example.

i want to take a subset of this data frame that has the lowest 20% of V3.

how this can be done 开发者_JS百科?

thanks for help

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The subset() function is handy because (among other benefits) it allows you to avoid having to repeatedly mention the name of the data-frame:

subset(dataFrame, V3 <= quantile(V3, 0.2))

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ss <- subset(dataFrame, subset=(dataFrame$V3 <= quantile(dataFrame$V3, 0.20)))