(This article was first published on

**Fear and Loathing in Data Science**, and kindly contributed to R-bloggers)Much to my chagrin, I realized I forgot to include one of the more interesting features in the lattice package. You can quickly turn a quantitative variable into one of levels of equal counts. This provides a nice way of looking at slices of your data in a trellis plot. These slices are referred to as shingles as they overlap according to your specification.

Here is a simple code example, using the quakes data included with R:

> library(lattice)

> head(quakes)

lat long depth mag stations

1 -20.42 181.62 562 4.8 41

2 -20.62 181.03 650 4.2 15

3 -26.00 184.10 42 5.4 43

4 -17.97 181.66 626 4.1 19

5 -20.42 181.96 649 4.0 11

6 -19.68 184.31 195 4.0 12

#Build an xyplot of lat and long conditioned by depth

> depth = quakes$depth

> range(depth)

[1] 40 680

> Depth = equal.count(depth, number=6, overlap=.05)

> # with equal.count we now have sliced depth into 6 parts with an overlap of 5%

plot(Depth)

xyplot(lat~long | Depth, data=quakes)

The way to read this plot is starting from the bottom left working right then the next row up from left to right.

Enjoy.

TDM

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