  Large matrices are often accessed as a row-order stream. We consider the
setting where rows are time-sensitive (i.e. they expire), which can be
described by the sliding-window row-order model, and provide the first
$(1+\epsilon)$-approximation of Schatten $p$-norms in this setting. Our main
technical contribution is a proof that Schatten $p$-norms in row-order streams
are smooth, and thus fit the smooth-histograms technique of Braverman and
Ostrovsky (FOCS 2007) for sliding-window streams.
