<s>
In	O
statistical	O
analysis	O
of	O
time	O
series	O
and	O
in	O
signal	O
processing	O
,	O
directional	B-Algorithm
symmetry	I-Algorithm
is	O
a	O
statistical	O
measure	O
of	O
a	O
model	O
's	O
performance	O
in	O
predicting	O
the	O
direction	O
of	O
change	O
,	O
positive	O
or	O
negative	O
,	O
of	O
a	O
time	O
series	O
from	O
one	O
time	O
period	O
to	O
the	O
next	O
.	O
</s>
