Formula for computing box plot whisker length

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reason180
Posts: 268
Joined: Mon Jul 24, 2017 4:56 pm

Formula for computing box plot whisker length

Post by reason180 »

Greetings all. Does anyone know what formula/rule jamovi uses for computing the lengths of the whiskers, in box plots?
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MAgojam
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Joined: Thu Jun 08, 2017 2:33 pm
Location: Parma (Italy)

Re: Formula for computing box plot whisker length

Post by MAgojam »

Depends on aesthetics in geom_boxplot(), package 'ggplot2'.
ymin (lower whisker = smallest observation greater than or equal to lower hinge - 1.5 * IQR)

ymax (upper whisker = largest observation less than or equal to upper hinge + 1.5 * IQR)

Cheers.
Maurizio
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Ravi
Posts: 194
Joined: Sat Jan 28, 2017 11:18 am

Re: Formula for computing box plot whisker length

Post by Ravi »

Exactly. From the geom_boxplot() documentation:
The upper whisker extends from the hinge to the largest value no further than 1.5 * IQR from the hinge (where IQR is the inter-quartile range, or distance between the first and third quartiles). The lower whisker extends from the hinge to the smallest value at most 1.5 * IQR of the hinge. Data beyond the end of the whiskers are called "outlying" points and are plotted individually.
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