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glamp/plyr_examples.R

Last active December 12, 2015 09:19
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plyr_examples.R
library(plyr)
# split a data frame by Species, summarize it, then convert the results
# into a data frame
ddply(iris, .(Species), summarise,
mean_petal_length=mean(Petal.Length)
)
# Species mean_petal_length
#1 setosa 1.462
#2 versicolor 4.260
#3 virginica 5.552
# split a data frame by Species, summarize it, then convert the results
# into an array
unlist(daply(iris[,4:5], .(Species), colwise(mean)))
# setosa.Petal.Width versicolor.Petal.Width virginica.Petal.Width
# 0.246 1.326 2.026
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