<s>
A	O
pie	B-Application
chart	I-Application
(	O
or	O
a	O
circle	B-Application
chart	I-Application
)	O
is	O
a	O
circular	O
statistical	B-Application
graphic	I-Application
,	O
which	O
is	O
divided	O
into	O
slices	O
to	O
illustrate	O
numerical	O
proportion	O
.	O
</s>
<s>
In	O
a	O
pie	B-Application
chart	I-Application
,	O
the	O
arc	O
length	O
of	O
each	O
slice	O
(	O
and	O
consequently	O
its	O
central	O
angle	O
and	O
area	O
)	O
is	O
proportional	O
to	O
the	O
quantity	O
it	O
represents	O
.	O
</s>
<s>
While	O
it	O
is	O
named	O
for	O
its	O
resemblance	O
to	O
a	O
pie	B-Application
which	O
has	O
been	O
sliced	O
,	O
there	O
are	O
variations	O
on	O
the	O
way	O
it	O
can	O
be	O
presented	O
.	O
</s>
<s>
The	O
earliest	O
known	O
pie	B-Application
chart	I-Application
is	O
generally	O
credited	O
to	O
William	O
Playfair	O
's	O
Statistical	O
Breviary	O
of	O
1801	O
.	O
</s>
<s>
Pie	B-Application
charts	I-Application
are	O
very	O
widely	O
used	O
in	O
the	O
business	O
world	O
and	O
the	O
mass	O
media	O
.	O
</s>
<s>
However	O
,	O
they	O
have	O
been	O
criticized	O
,	O
and	O
many	O
experts	O
recommend	O
avoiding	O
them	O
,	O
as	O
research	O
has	O
shown	O
it	O
is	O
difficult	O
to	O
compare	O
different	O
sections	O
of	O
a	O
given	O
pie	B-Application
chart	I-Application
,	O
or	O
to	O
compare	O
data	O
across	O
different	O
pie	B-Application
charts	I-Application
.	O
</s>
<s>
Pie	B-Application
charts	I-Application
can	O
be	O
replaced	O
in	O
most	O
cases	O
by	O
other	O
plots	O
such	O
as	O
the	O
bar	B-Application
chart	I-Application
,	O
box	B-Application
plot	I-Application
,	O
dot	B-Application
plot	I-Application
,	O
etc	O
.	O
</s>
<s>
The	O
earliest	O
known	O
pie	B-Application
chart	I-Application
is	O
generally	O
credited	O
to	O
William	O
Playfair	O
's	O
Statistical	O
Breviary	O
of	O
1801	O
,	O
in	O
which	O
two	O
such	O
graphs	O
are	O
used	O
.	O
</s>
<s>
Playfair	O
presented	O
an	O
illustration	O
,	O
which	O
contained	O
a	O
series	O
of	O
pie	B-Application
charts	I-Application
.	O
</s>
<s>
Playfair	O
thought	O
that	O
pie	B-Application
charts	I-Application
were	O
in	O
need	O
of	O
a	O
third	O
dimension	O
to	O
add	O
additional	O
information	O
.	O
</s>
<s>
Florence	O
Nightingale	O
may	O
not	O
have	O
invented	O
the	O
pie	B-Application
chart	I-Application
,	O
but	O
she	O
adapted	O
it	O
to	O
make	O
it	O
more	O
readable	O
,	O
which	O
fostered	O
its	O
wide	O
use	O
,	O
still	O
today	O
.	O
</s>
<s>
Indeed	O
,	O
Nightingale	O
reconfigured	O
the	O
pie	B-Application
chart	I-Application
making	O
the	O
length	O
of	O
the	O
wedges	O
variable	O
instead	O
of	O
their	O
width	O
.	O
</s>
<s>
Nightingale	O
's	O
polar	O
area	O
diagram	O
,	O
or	O
occasionally	O
the	O
Nightingale	O
rose	O
diagram	O
,	O
equivalent	O
to	O
a	O
modern	O
circular	O
histogram	B-Algorithm
,	O
to	O
illustrate	O
seasonal	O
sources	O
of	O
patient	O
mortality	O
in	O
the	O
military	O
field	O
hospital	O
she	O
managed	O
,	O
was	O
published	O
in	O
Notes	O
on	O
Matters	O
Affecting	O
the	O
Health	O
,	O
Efficiency	O
,	O
and	O
Hospital	O
Administration	O
of	O
the	O
British	O
Army	O
and	O
sent	O
to	O
Queen	O
Victoria	O
in	O
1858	O
.	O
</s>
<s>
The	O
French	O
engineer	O
Charles	O
Joseph	O
Minard	O
also	O
used	O
pie	B-Application
charts	I-Application
,	O
in	O
1858	O
.	O
</s>
<s>
A	O
map	O
of	O
his	O
from	O
1858	O
used	O
pie	B-Application
charts	I-Application
to	O
represent	O
the	O
cattle	O
sent	O
from	O
all	O
around	O
France	O
for	O
consumption	O
in	O
Paris	O
.	O
</s>
<s>
A	O
3D	O
pie	B-Application
chart	I-Application
,	O
or	O
perspective	B-Architecture
pie	B-Application
chart	I-Application
,	O
is	O
used	O
to	O
give	O
the	O
chart	O
a	O
3D	O
look	O
.	O
</s>
<s>
Often	O
used	O
for	O
aesthetic	O
reasons	O
,	O
the	O
third	O
dimension	O
does	O
not	O
improve	O
the	O
reading	O
of	O
the	O
data	O
;	O
on	O
the	O
contrary	O
,	O
these	O
plots	O
are	O
difficult	O
to	O
interpret	O
because	O
of	O
the	O
distorted	O
effect	O
of	O
perspective	B-Architecture
associated	O
with	O
the	O
third	O
dimension	O
.	O
</s>
<s>
The	O
use	O
of	O
superfluous	O
dimensions	O
not	O
used	O
to	O
display	O
the	O
data	O
of	O
interest	O
is	O
discouraged	O
for	O
charts	O
in	O
general	O
,	O
not	O
only	O
for	O
pie	B-Application
charts	I-Application
.	O
</s>
<s>
A	O
doughnut	O
chart	O
(	O
also	O
spelled	O
donut	O
)	O
is	O
a	O
variant	O
of	O
the	O
pie	B-Application
chart	I-Application
,	O
with	O
a	O
blank	O
center	O
allowing	O
for	O
additional	O
information	O
about	O
the	O
data	O
as	O
a	O
whole	O
to	O
be	O
included	O
.	O
</s>
<s>
Doughnut	O
charts	O
are	O
similar	O
to	O
pie	B-Application
charts	I-Application
in	O
that	O
their	O
aim	O
is	O
to	O
illustrate	O
proportions	O
.	O
</s>
<s>
This	O
type	O
of	O
circular	O
graph	O
can	O
support	O
multiple	O
statistics	O
at	O
once	O
and	O
it	O
provides	O
a	O
better	O
data	O
intensity	O
ratio	O
to	O
standard	O
pie	B-Application
charts	I-Application
.	O
</s>
<s>
A	O
chart	O
with	O
one	O
or	O
more	O
sectors	O
separated	O
from	O
the	O
rest	O
of	O
the	O
disk	O
is	O
known	O
as	O
an	O
exploded	O
pie	B-Application
chart	I-Application
.	O
</s>
<s>
The	O
polar	O
area	O
diagram	O
is	O
similar	O
to	O
a	O
usual	O
pie	B-Application
chart	I-Application
,	O
except	O
sectors	O
have	O
equal	O
angles	O
and	O
differ	O
rather	O
in	O
how	O
far	O
each	O
sector	O
extends	O
from	O
the	O
center	O
of	O
the	O
circle	O
.	O
</s>
<s>
A	O
ring	O
chart	O
,	O
also	O
known	O
as	O
a	O
sunburst	O
chart	O
or	O
a	O
multilevel	O
pie	B-Application
chart	I-Application
,	O
is	O
used	O
to	O
visualize	O
hierarchical	O
data	O
,	O
depicted	O
by	O
concentric	O
circles	O
.	O
</s>
<s>
The	O
design	O
superimposes	O
a	O
normal	O
pie	B-Application
chart	I-Application
with	O
a	O
modified	O
polar	O
area	O
chart	O
to	O
permit	O
the	O
comparison	O
of	O
two	O
sets	O
of	O
related	O
data	O
.	O
</s>
<s>
The	O
base	O
pie	B-Application
chart	I-Application
represents	O
the	O
first	O
data	O
set	O
in	O
the	O
usual	O
way	O
,	O
with	O
different	O
slice	O
sizes	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
base	O
pie	B-Application
chart	I-Application
could	O
show	O
the	O
distribution	O
of	O
age	O
and	O
gender	O
groups	O
in	O
a	O
population	O
,	O
and	O
the	O
overlay	O
their	O
representation	O
among	O
road	O
casualties	O
.	O
</s>
<s>
Age	O
and	O
gender	O
groups	O
that	O
are	O
especially	O
susceptible	O
to	O
being	O
involved	O
in	O
accidents	O
then	O
stand	O
out	O
as	O
slices	O
that	O
extend	O
beyond	O
the	O
original	O
pie	B-Application
chart	I-Application
.	O
</s>
<s>
Square	O
charts	O
,	O
also	O
called	O
waffle	O
charts	O
,	O
are	O
a	O
form	O
of	O
pie	B-Application
charts	I-Application
that	O
use	O
squares	O
instead	O
of	O
circles	O
to	O
represent	O
percentages	O
.	O
</s>
<s>
Similar	O
to	O
basic	O
circular	O
pie	B-Application
charts	I-Application
,	O
square	O
pie	B-Application
charts	I-Application
take	O
each	O
percentage	O
out	O
of	O
a	O
total	O
100%	O
.	O
</s>
<s>
One	O
major	O
benefit	O
to	O
square	O
charts	O
is	O
that	O
smaller	O
percentages	O
,	O
difficult	O
to	O
see	O
on	O
traditional	O
pie	B-Application
charts	I-Application
,	O
can	O
be	O
easily	O
depicted	O
.	O
</s>
<s>
*	O
Because	O
of	O
rounding	B-Algorithm
,	O
these	O
totals	O
do	O
not	O
add	O
up	O
to	O
100	O
and	O
360	O
.	O
</s>
<s>
A	O
flaw	O
exhibited	O
by	O
pie	B-Application
charts	I-Application
is	O
that	O
they	O
cannot	O
show	O
more	O
than	O
a	O
few	O
values	O
without	O
separating	O
the	O
visual	O
encoding	O
(	O
the	O
“	O
slices	O
”	O
)	O
from	O
the	O
data	O
they	O
represent	O
(	O
typically	O
percentages	O
)	O
.	O
</s>
<s>
When	O
slices	O
become	O
too	O
small	O
,	O
pie	B-Application
charts	I-Application
have	O
to	O
rely	O
on	O
colors	O
,	O
textures	O
or	O
arrows	O
so	O
the	O
reader	O
can	O
understand	O
them	O
.	O
</s>
<s>
Pie	B-Application
charts	I-Application
also	O
take	O
up	O
a	O
larger	O
amount	O
of	O
space	O
on	O
the	O
page	O
compared	O
to	O
the	O
more	O
flexible	O
bar	B-Application
charts	I-Application
,	O
which	O
do	O
not	O
need	O
to	O
have	O
separate	O
legends	O
,	O
and	O
can	O
display	O
other	O
values	O
such	O
as	O
averages	O
or	O
targets	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
Statisticians	O
generally	O
regard	O
pie	B-Application
charts	I-Application
as	O
a	O
poor	O
method	O
of	O
displaying	O
information	O
,	O
and	O
they	O
are	O
uncommon	O
in	O
scientific	O
literature	O
.	O
</s>
<s>
Most	O
subjects	O
have	O
difficulty	O
ordering	O
the	O
slices	O
in	O
the	O
pie	B-Application
chart	I-Application
by	O
size	O
;	O
when	O
an	O
equivalent	O
bar	B-Application
chart	I-Application
is	O
used	O
the	O
comparison	O
is	O
much	O
easier	O
.	O
</s>
<s>
Similarly	O
,	O
comparisons	O
between	O
data	O
sets	O
are	O
easier	O
using	O
the	O
bar	B-Application
chart	I-Application
.	O
</s>
<s>
However	O
,	O
if	O
the	O
goal	O
is	O
to	O
compare	O
a	O
given	O
category	O
(	O
a	O
slice	O
of	O
the	O
pie	B-Application
)	O
with	O
the	O
total	O
(	O
the	O
whole	O
pie	B-Application
)	O
in	O
a	O
single	O
chart	O
and	O
the	O
multiple	O
is	O
close	O
to	O
25	O
or	O
50	O
percent	O
,	O
then	O
a	O
pie	B-Application
chart	I-Application
can	O
often	O
be	O
more	O
effective	O
than	O
a	O
bar	B-Application
graph	I-Application
.	O
</s>
<s>
In	O
a	O
pie	B-Application
chart	I-Application
with	O
many	O
section	O
,	O
several	O
values	O
may	O
be	O
represented	O
with	O
the	O
same	O
or	O
similar	O
colors	O
,	O
making	O
interpretation	O
difficult	O
.	O
</s>
<s>
Several	O
studies	O
presented	O
at	O
the	O
European	O
Visualization	O
Conference	O
analyzed	O
the	O
relative	O
accuracy	O
of	O
several	O
pie	B-Application
chart	I-Application
formats	O
,	O
reaching	O
the	O
conclusion	O
that	O
pie	B-Application
charts	I-Application
and	O
doughnut	O
charts	O
produce	O
similar	O
error	O
levels	O
when	O
reading	O
them	O
,	O
and	O
square	O
pie	B-Application
charts	I-Application
provide	O
the	O
most	O
accurate	O
reading	O
.	O
</s>
