identifying outliers

Hi

You can check boxplot output by str

iris[1,1] <- 10
iris[2,1] <- 8
bbb <- boxplot(split(iris[,1], iris$Species))
str(bbb)

List of 6
 $ stats: num [1:5, 1:3] 4.3 4.8 5 5.3 5.8 4.9 5.6 5.9 6.3 7 ...
 $ n    : num [1:3] 50 50 50
 $ conf : num [1:2, 1:3] 4.89 5.11 5.74 6.06 6.34 ...
 $ out  : num [1:3] 10 8 4.9
 $ group: num [1:3] 1 1 3
 $ names: chr [1:3] "setosa" "versicolor" "virginica"

and you can find that result is list with out vector containing all outliers and group vector of indication to which group outliers belong.

Getting the output depends on what you want to do with it.

Cheers
Petr

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Thomas
Subia via R-help
Sent: Thursday, April 7, 2016 6:10 AM
To: r-help at stat.math.ethz.ch
Subject: [R] identifying outliers

Thanks for writing this great piece of code.



x = rnorm(100)

boxplot(x) # you shouldn't see any outliers here although sometimes yow
will



# lets add some outliers intentionally

x = c(21, 20, 25, x) # now 10, 15 and 20 are outliers



myboxplot <- boxplot(x) # now you should see your three outliers



myboxplot$out # it will print the values of the outliers



How does one amend this code to produce the outliers by a group?



All the best,



Thomas Subia


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