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Formula for computing box plot whisker length
Posted: Fri Jan 12, 2018 1:22 am
by reason180
Greetings all. Does anyone know what formula/rule jamovi uses for computing the lengths of the whiskers, in box plots?
Re: Formula for computing box plot whisker length
Posted: Fri Jan 12, 2018 6:05 pm
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
Re: Formula for computing box plot whisker length
Posted: Fri Jan 12, 2018 6:10 pm
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.