<s>
In	O
mathematics	O
,	O
a	O
ridge	B-Algorithm
function	I-Algorithm
is	O
any	O
function	O
that	O
can	O
be	O
written	O
as	O
the	O
composition	O
of	O
a	O
univariate	B-General_Concept
function	O
with	O
an	O
affine	B-Algorithm
transformation	I-Algorithm
,	O
that	O
is	O
:	O
for	O
some	O
and	O
.	O
</s>
<s>
Coinage	O
of	O
the	O
term	O
'	O
ridge	B-Algorithm
function	I-Algorithm
 '	O
is	O
often	O
attributed	O
to	O
B.F.	O
Logan	O
and	O
L.A.	O
Shepp	O
.	O
</s>
<s>
A	O
ridge	B-Algorithm
function	I-Algorithm
is	O
not	O
susceptible	O
to	O
the	O
curse	B-Algorithm
of	I-Algorithm
dimensionality	I-Algorithm
,	O
making	O
it	O
an	O
instrumental	O
tool	O
in	O
various	O
estimation	O
problems	O
.	O
</s>
<s>
This	O
is	O
a	O
direct	O
result	O
of	O
the	O
fact	O
that	O
ridge	B-Algorithm
functions	I-Algorithm
are	O
constant	O
in	O
directions	O
:	O
</s>
<s>
Ridge	B-Algorithm
functions	I-Algorithm
play	O
an	O
essential	O
role	O
in	O
amongst	O
others	O
projection	B-General_Concept
pursuit	I-General_Concept
,	O
generalized	O
linear	O
models	O
,	O
and	O
as	O
activation	B-Algorithm
functions	I-Algorithm
in	O
neural	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
For	O
a	O
survey	O
on	O
ridge	B-Algorithm
functions	I-Algorithm
,	O
see	O
.	O
</s>
<s>
For	O
books	O
on	O
ridge	B-Algorithm
functions	I-Algorithm
,	O
see	O
.	O
</s>
