<s>
In	O
statistics	O
,	O
the	O
relationship	B-Algorithm
square	I-Algorithm
is	O
a	O
graphical	O
representation	O
for	O
use	O
in	O
the	O
factorial	O
analysis	O
of	O
a	O
table	O
individuals	O
x	O
variables	O
.	O
</s>
<s>
This	O
representation	O
completes	O
classical	O
representations	O
provided	O
by	O
principal	B-Application
component	I-Application
analysis	I-Application
(	O
PCA	O
)	O
or	O
multiple	B-Algorithm
correspondence	I-Algorithm
analysis	I-Algorithm
(	O
MCA	O
)	O
,	O
namely	O
those	O
of	O
individuals	O
,	O
of	O
quantitative	O
variables	O
(	O
correlation	O
circle	O
)	O
and	O
of	O
the	O
categories	O
of	O
qualitative	O
variables	O
(	O
at	O
the	O
centroid	O
of	O
the	O
individuals	O
who	O
possess	O
them	O
)	O
.	O
</s>
<s>
It	O
is	O
especially	O
important	O
in	O
factor	B-Algorithm
analysis	I-Algorithm
of	I-Algorithm
mixed	I-Algorithm
data	I-Algorithm
(	O
FAMD	O
)	O
and	O
in	O
multiple	O
factor	O
analysis	O
(	O
MFA	O
)	O
.	O
</s>
<s>
The	O
first	O
interest	O
of	O
the	O
relationship	B-Algorithm
square	I-Algorithm
is	O
to	O
represent	O
the	O
variables	O
themselves	O
,	O
not	O
their	O
categories	O
,	O
which	O
is	O
all	O
the	O
more	O
valuable	O
as	O
there	O
are	O
many	O
variables	O
.	O
</s>
<s>
For	O
this	O
,	O
we	O
calculate	O
for	O
each	O
qualitative	O
variable	O
and	O
each	O
factor	O
(	O
,	O
rank	O
factor	O
,	O
is	O
the	O
vector	O
of	O
coordinates	O
of	O
the	O
individuals	O
along	O
the	O
axis	O
of	O
rank	O
;	O
in	O
PCA	O
,	O
is	O
called	O
principal	B-Application
component	I-Application
of	O
rank	O
)	O
,	O
the	O
square	O
of	O
the	O
correlation	O
ratio	O
between	O
the	O
and	O
the	O
variable	O
,	O
usually	O
denoted	O
:	O
</s>
<s>
Relationship	B-Algorithm
square	I-Algorithm
.	O
</s>
<s>
The	O
relationship	B-Algorithm
square	I-Algorithm
(	O
Figure	O
2	O
)	O
makes	O
easier	O
the	O
reading	O
of	O
the	O
classic	O
factorial	O
plane	O
.	O
</s>
<s>
The	O
role	O
of	O
the	O
relationship	B-Algorithm
square	I-Algorithm
is	O
first	O
to	O
assist	O
in	O
reading	O
a	O
conventional	O
graphic	O
.	O
</s>
<s>
Thus	O
,	O
the	O
second	O
advantage	O
of	O
the	O
relationship	B-Algorithm
square	I-Algorithm
lies	O
in	O
the	O
ability	O
to	O
represent	O
simultaneously	O
quantitative	O
and	O
qualitative	O
variables	O
.	O
</s>
<s>
The	O
relationship	B-Algorithm
square	I-Algorithm
can	O
be	O
constructed	O
from	O
any	O
factorial	O
analysis	O
of	O
a	O
table	O
individuals	O
x	O
variables	O
.	O
</s>
<s>
in	O
principal	B-Application
components	I-Application
analysis	I-Application
(	O
PCA	O
)	O
when	O
there	O
are	O
many	O
supplementary	O
variables	O
;	O
</s>
<s>
in	O
factor	B-Algorithm
analysis	I-Algorithm
of	I-Algorithm
mixed	I-Algorithm
data	I-Algorithm
(	O
FAMD	O
)	O
.	O
</s>
<s>
In	O
MCA	O
,	O
the	O
relationship	B-Algorithm
square	I-Algorithm
provides	O
a	O
synthetic	O
view	O
of	O
the	O
connections	O
between	O
mixed	O
variables	O
,	O
all	O
the	O
more	O
valuable	O
as	O
there	O
are	O
many	O
variables	O
having	O
many	O
categories	O
.	O
</s>
