Database Reference
In-Depth Information
Figure 5.4
Scatterplot matrix on the support, confidence, and lift of the 2,918
rules
Figure 5.4
shows that lift is proportional to confidence and illustrates several
linear groupings. As indicated by
Equation 5.2
and
Equation 5.3
,
. Therefore, when the support of Y remains the
same, lift is proportional to confidence, and the slope of the linear trend is the
reciprocal of
. The following code shows that, of the 2,918 rules, there
are only 18 different values for
, and the majority occurs at slopes 3.91,
5.17, 7.17, 9.17, and 9.53. This matches the slopes shown in the third row and
second column of
Figure 5.4
,
where the x-axis is the confidence and the y-axis is
the lift.
# compute the 1/Support(Y)
slope <- sort(round(rules@quality$lift /
rules@quality$confidence, 2))
# Display the number of times each slope appears in the
dataset
unlist(lapply(split(slope,f=slope),length))
3.91 5.17 5.44 5.73 7.17 9.05 9.17 9.53 10.64 12.08
1585 940 12 7 188 1 102 55 1 4
12.42 13.22 13.83 13.95 18.05 23.76 26.44 30.08
1 5 2 9 3 1 1 1
