[R] Calculate Range

[jlh.membership]

An approach using data tables:

###
library(data.table)
# dt: some data arranged by group
dt <- data.table(group=c(rep("a",5), rep("b",10), rep("c",15)), values=1:30)
# summarize by group
smry <- dt[,list(min=min(values), max=max(values), range=diff(range(values))), by="group"]
smry
###


-----Original Message-----
From: SCRIPTHAM [mailto:JML at CWAZY.CO.UK] 
Sent: Saturday, November 16, 2013 4:50 PM
To: r-help at r-project.org
Subject: [R] Calculate Range

Hi

My R version is the current version as at 15 Nov 2013.

I have tried to calculate range using tapply() with FUN=range.
tapply() returns two fields, the ID field and a field of two text items one is the maximum and the other is the minimum.
I take as the difference max - min, does R use a different term for range in tapply?

I have also tried
aggregate() with Fun=range, with Fun=min and FUN=max and they also gave problems.

What is the best route to calculate ranges for groups within a data frame.

Thanks.
Scriptham.






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