<s>
Binary	B-General_Concept
classification	I-General_Concept
is	O
the	O
task	O
of	O
classifying	B-General_Concept
the	O
elements	O
of	O
a	O
set	O
into	O
two	O
groups	O
(	O
each	O
called	O
class	O
)	O
on	O
the	O
basis	O
of	O
a	O
classification	B-General_Concept
rule	I-General_Concept
.	O
</s>
<s>
Typical	O
binary	B-General_Concept
classification	I-General_Concept
problems	O
include	O
:	O
</s>
<s>
In	O
information	B-Library
retrieval	I-Library
,	O
deciding	O
whether	O
a	O
page	O
should	O
be	O
in	O
the	O
result	B-Application
set	I-Application
of	O
a	O
search	O
or	O
not	O
.	O
</s>
<s>
Binary	B-General_Concept
classification	I-General_Concept
is	O
dichotomization	B-Algorithm
applied	O
to	O
a	O
practical	O
situation	O
.	O
</s>
<s>
In	O
many	O
practical	O
binary	B-General_Concept
classification	I-General_Concept
problems	O
,	O
the	O
two	O
groups	O
are	O
not	O
symmetric	O
,	O
and	O
rather	O
than	O
overall	O
accuracy	O
,	O
the	O
relative	O
proportion	O
of	O
different	O
types	O
of	O
errors	O
is	O
of	O
interest	O
.	O
</s>
<s>
Statistical	B-General_Concept
classification	I-General_Concept
is	O
a	O
problem	O
studied	O
in	O
machine	O
learning	O
.	O
</s>
<s>
It	O
is	O
a	O
type	O
of	O
supervised	B-General_Concept
learning	I-General_Concept
,	O
a	O
method	O
of	O
machine	O
learning	O
where	O
the	O
categories	O
are	O
predefined	O
,	O
and	O
is	O
used	O
to	O
categorize	O
new	O
probabilistic	O
observations	O
into	O
said	O
categories	O
.	O
</s>
<s>
When	O
there	O
are	O
only	O
two	O
categories	O
the	O
problem	O
is	O
known	O
as	O
statistical	O
binary	B-General_Concept
classification	I-General_Concept
.	O
</s>
<s>
Some	O
of	O
the	O
methods	O
commonly	O
used	O
for	O
binary	B-General_Concept
classification	I-General_Concept
are	O
:	O
</s>
<s>
Each	O
classifier	B-General_Concept
is	O
best	O
in	O
only	O
a	O
select	O
domain	O
based	O
upon	O
the	O
number	O
of	O
observations	O
,	O
the	O
dimensionality	O
of	O
the	O
feature	B-Algorithm
vector	I-Algorithm
,	O
the	O
noise	O
in	O
the	O
data	O
and	O
many	O
other	O
factors	O
.	O
</s>
<s>
For	O
example	O
,	O
random	B-Algorithm
forests	I-Algorithm
perform	O
better	O
than	O
SVM	B-Algorithm
classifiers	B-General_Concept
for	O
3D	O
point	O
clouds	O
.	O
</s>
<s>
There	O
are	O
many	O
metrics	O
that	O
can	O
be	O
used	O
to	O
measure	O
the	O
performance	O
of	O
a	O
classifier	B-General_Concept
or	O
predictor	O
;	O
different	O
fields	O
have	O
different	O
preferences	O
for	O
specific	O
metrics	O
due	O
to	O
different	O
goals	O
.	O
</s>
<s>
In	O
medicine	O
sensitivity	O
and	O
specificity	O
are	O
often	O
used	O
,	O
while	O
in	O
information	B-Library
retrieval	I-Library
precision	O
and	O
recall	O
are	O
preferred	O
.	O
</s>
<s>
These	O
can	O
be	O
arranged	O
into	O
a	O
2×2	O
contingency	B-Application
table	I-Application
,	O
with	O
columns	O
corresponding	O
to	O
actual	O
value	O
–	O
condition	O
positive	O
or	O
condition	O
negative	O
–	O
and	O
rows	O
corresponding	O
to	O
classification	O
value	O
–	O
test	O
outcome	O
positive	O
or	O
test	O
outcome	O
negative	O
.	O
</s>
<s>
The	O
F-score	B-General_Concept
combines	O
precision	O
and	O
recall	O
into	O
one	O
number	O
via	O
a	O
choice	O
of	O
weighing	O
,	O
most	O
simply	O
equal	O
weighing	O
,	O
as	O
the	O
balanced	O
F-score	B-General_Concept
(	O
F1	B-General_Concept
score	I-General_Concept
)	O
.	O
</s>
<s>
Some	O
metrics	O
come	O
from	O
regression	B-General_Concept
coefficients	I-General_Concept
:	O
the	O
markedness	O
and	O
the	O
informedness	B-General_Concept
,	O
and	O
their	O
geometric	O
mean	O
,	O
the	O
Matthews	B-General_Concept
correlation	I-General_Concept
coefficient	I-General_Concept
.	O
</s>
<s>
Other	O
metrics	O
include	O
Youden	B-General_Concept
's	I-General_Concept
J	I-General_Concept
statistic	I-General_Concept
,	O
the	O
uncertainty	O
coefficient	O
,	O
the	O
phi	B-General_Concept
coefficient	I-General_Concept
,	O
and	O
Cohen	B-General_Concept
's	I-General_Concept
kappa	I-General_Concept
.	O
</s>
<s>
However	O
,	O
such	O
conversion	O
causes	O
a	O
loss	O
of	O
information	O
,	O
as	O
the	O
resultant	O
binary	B-General_Concept
classification	I-General_Concept
does	O
not	O
tell	O
how	O
much	O
above	O
or	O
below	O
the	O
cutoff	O
a	O
value	O
is	O
.	O
</s>
