adjboxStats  R Documentation 
Computes the “statistics” for producing boxplots adjusted for
skewed distributions as proposed in Hubert and Vandervieren (2008),
see adjbox
.
adjboxStats(x, coef = 1.5, a = 4, b = 3, do.conf = TRUE, do.out = TRUE,
...)
x 
a numeric vector for which adjusted boxplot statistics are computed. 
coef 
number determining how far ‘whiskers’ extend out
from the box, see 
a, b 
scaling factors multiplied by the medcouple

do.conf,do.out 
logicals; if 
... 
further optional arguments to be passed to

Given the quartiles Q_1
, Q_3
, the interquartile
range \Delta Q := Q_3  Q_1
, and the medcouple
M :=
mc(x)
, c =
coef
,
the “fence” is defined,
for M \ge 0
as
[Q_1  c e^{a \cdot M}\Delta Q, Q_3 + c e^{b \cdot M}\Delta Q],%
and for M < 0
as
[Q_1  c e^{b \cdot M}\Delta Q, Q_3 + c e^{a \cdot M}\Delta Q],%
and all observations x
outside the fence, the “potential
outliers”, are returned in out
.
Note that a typo in robustbase version up to 0.78, for the (rare leftskewed) case where mc(x) < 0, lead to a “fence” not wide enough in the upper part, and hence less outliers there.
A list
with the components
stats 
a vector of length 5, containing the extreme of the lower whisker, the lower hinge, the median, the upper hinge and the extreme of the upper whisker. 
n 
the number of observations 
conf 
the lower and upper extremes of the ‘notch’
( 
fence 
length 2 vector of interval boundaries which define the nonoutliers, and hence the whiskers of the plot. 
out 
the values of any data points which lie beyond the fence, and hence beyond the extremes of the whiskers. 
The code only slightly modifies the code of R's
boxplot.stats
.
R Core Development Team (boxplot.stats
); adapted
by Tobias Verbeke and Martin Maechler.
adjbox()
, also for references,
the function which mainly uses this one;
further boxplot.stats
.
data(condroz)
adjboxStats(ccA < condroz[,"Ca"])
adjboxStats(ccA, doReflect = TRUE)# small difference in fence
## Test reflection invariance [was not ok, up to and including robustbase_0.78]
a1 < adjboxStats( ccA, doReflect = TRUE)
a2 < adjboxStats(ccA, doReflect = TRUE)
nm1 < c("stats", "conf", "fence")
stopifnot(all.equal( a1[nm1],
lapply(a2[nm1], function(u) rev(u))),
all.equal(a1[["out"]], a2[["out"]]))
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