<s>
In	O
machine	O
learning	O
,	O
a	O
nearest	B-Algorithm
centroid	I-Algorithm
classifier	I-Algorithm
or	O
nearest	B-Algorithm
prototype	I-Algorithm
classifier	I-Algorithm
is	O
a	O
classification	B-General_Concept
model	I-General_Concept
that	O
assigns	O
to	O
observations	O
the	O
label	O
of	O
the	O
class	O
of	O
training	O
samples	O
whose	O
mean	O
(	O
centroid	O
)	O
is	O
closest	O
to	O
the	O
observation	O
.	O
</s>
<s>
When	O
applied	O
to	O
text	B-Algorithm
classification	I-Algorithm
using	O
word	O
vectors	O
containing	O
tf*idf	O
weights	O
to	O
represent	O
documents	O
,	O
the	O
nearest	B-Algorithm
centroid	I-Algorithm
classifier	I-Algorithm
is	O
known	O
as	O
the	O
Rocchio	O
classifier	B-General_Concept
because	O
of	O
its	O
similarity	O
to	O
the	O
Rocchio	B-Algorithm
algorithm	I-Algorithm
for	O
relevance	B-Application
feedback	I-Application
.	O
</s>
<s>
An	O
extended	O
version	O
of	O
the	O
nearest	B-Algorithm
centroid	I-Algorithm
classifier	I-Algorithm
has	O
found	O
applications	O
in	O
the	O
medical	O
domain	O
,	O
specifically	O
classification	O
of	O
tumors	O
.	O
</s>
