Graph does not show after type lattice command

I installed the package lattice, and typed xyplot(). There is no error message but neither does a graph show u开发者_JS百科p. I tried to switch to plot() and it works well. Any idea why it happened? Thank you!

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Try this:

require(lattice)
require(stats)

Depth <- equal.count(quakes$depth, number=8, overlap=.1)
my_plot <- xyplot(lat ~ long | Depth, data = quakes)
print(my_plot)

Thanks to richiemorrisroe and Gavin Simpson.