youden {spatstat.explore} | R Documentation |
Youden Statistic
Description
Calculate the Youden statistic for an ROC curve.
Usage
youden(X, sign = c("positive", "absolute", "negative"))
Arguments
X |
ROC curve (object of class |
sign |
Character string indicating which version of the statistic to calculate. |
Details
For a receiver operating characteristic (ROC) curve, the
Youden statistic is the maximum vertical deviation between the curve
and the diagonal line y=x
.
Suppose R(p)
denotes the ROC curve as a function of the
horizontal coordinate p
.
If sign="positive"
(the default), deviation is defined as the
positive part \max(0, R(p)-p)
.
If sign="absolute"
, deviation is defined as the
absolute value | R(p) - p|
.
If sign="negative"
, deviation is defined as the
negative part \max(0, p - R(p))
.
The maximum deviation over all values of p
is determined.
The result is always nonnegative.
Value
Numeric value or vector, containing nonnegative values.
Author(s)
Adrian Baddeley Adrian.Baddeley@curtin.edu.au.
References
Youden, W.J. (1950) Index for rating diagnostic tests. Cancer 3, 32–35.
See Also
Examples
a <- with(split(mucosa), roc(ECL, "y", baseline=other, high=FALSE))
youden(a)