<s>
The	O
canopy	B-Algorithm
clustering	I-Algorithm
algorithm	I-Algorithm
is	O
an	O
unsupervised	O
pre-clustering	O
algorithm	O
introduced	O
by	O
Andrew	O
McCallum	O
,	O
Kamal	O
Nigam	O
and	O
Lyle	O
Ungar	O
in	O
2000	O
.	O
</s>
<s>
It	O
is	O
often	O
used	O
as	O
preprocessing	O
step	O
for	O
the	O
K-means	B-Algorithm
algorithm	I-Algorithm
or	O
the	O
Hierarchical	B-Algorithm
clustering	I-Algorithm
algorithm	O
.	O
</s>
<s>
It	O
is	O
intended	O
to	O
speed	O
up	O
clustering	B-Architecture
operations	O
on	O
large	O
data	B-General_Concept
sets	I-General_Concept
,	O
where	O
using	O
another	O
algorithm	O
directly	O
may	O
be	O
impractical	O
due	O
to	O
the	O
size	O
of	O
the	O
data	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
Begin	O
with	O
the	O
set	B-General_Concept
of	I-General_Concept
data	I-General_Concept
points	O
to	O
be	O
clustered	O
.	O
</s>
<s>
Since	O
the	O
algorithm	O
uses	O
distance	O
functions	O
and	O
requires	O
the	O
specification	O
of	O
distance	O
thresholds	O
,	O
its	O
applicability	O
for	O
high-dimensional	O
data	O
is	O
limited	O
by	O
the	O
curse	B-Algorithm
of	I-Algorithm
dimensionality	I-Algorithm
.	O
</s>
<s>
Only	O
when	O
a	O
cheap	O
and	O
approximative	O
–	O
low-dimensional	O
–	O
distance	O
function	O
is	O
available	O
,	O
the	O
produced	O
canopies	O
will	O
preserve	O
the	O
clusters	O
produced	O
by	O
K-means	B-Algorithm
.	O
</s>
