Data manipulations
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In the last Utah R Users group meeting I gave a presentation on data manipulations on R, and today I found through the plyr mailing list two commands that I was previously unaware of that should definitely be made mention of.
arrange
I was very pleased to find arrange because it fills the nagging hole for sorting data frames. Calling
arrange(df, var1, var2)
is much better than calling
df[order(df$var1, df$var2),]
because it’s understandable by practically anyone, and when your code is understandable there is less chance of mistakes.
mutate
mutate is not that different from transform, but I have to make the confession that when I was setting things up for my presentation I tried to see if transform could do the things that mutate does. mutate can include previously defined variables in later defined variables. I quote from the mutate help file,
# Things transform can't do mutate(airquality, Temp = (Temp - 32) / 1.8, OzT = Ozone / Temp)
Notice that temp is first defined then used. Usually when I need to do something like that I resort to using within, but hopefully I will have to do that less now.
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