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Mike Bostock
Visualization toolmaker. Founder @observablehq. Creator @d3. Former @nytgraphics. Pronounced BOSS-tock.
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Data Analysis
By
Mike Bostock
Edited
Oct 20, 2018
Importers
22 stars
Data Analysis
Manipulating Flat Arrays
Nested Groups
Group
Insert cell
Insert cell
data
=
[
{
name
:
"jim"
,
amount
:
"34.0"
,
date
:
"11/12/2015"
}
,
{
name
:
"carl"
,
amount
:
"120.11"
,
date
:
"11/12/2015"
}
,
{
name
:
"stacy"
,
amount
:
"12.01"
,
date
:
"01/04/2016"
}
,
{
name
:
"stacy"
,
amount
:
"34.05"
,
date
:
"01/04/2016"
}
]
Insert cell
Insert cell
new
Map
(
Array
.
from
(
group
(
data
,
d
=>
d
.
name
)
,
(
[
name
,
data
]
)
=>
[
name
,
group
(
data
,
d
=>
d
.
date
)
]
)
)
Insert cell
Insert cell
function
nest
(
values
,
...
keys
)
{
return
(
function
regroup
(
values
,
i
)
{
if
(
i
>=
keys
.
length
)
return
values
;
const
map
=
group
(
values
,
keys
[
i
]
)
;
return
new
Map
(
Array
.
from
(
map
,
(
[
k
,
v
]
)
=>
[
k
,
regroup
(
v
,
i
+
1
)
]
)
)
;
}
)
(
values
,
0
)
;
}
Insert cell
nest
(
data
,
d
=>
d
.
name
,
d
=>
d
.
date
)
Insert cell
nest
(
data
,
d
=>
d
.
name
)
Insert cell
nest
(
data
)
Insert cell
Insert cell
function
rollup
(
values
,
reduce
,
...
keys
)
{
return
(
function
regroup
(
values
,
i
)
{
if
(
i
>=
keys
.
length
)
return
reduce
(
values
)
;
const
map
=
group
(
values
,
keys
[
i
]
)
;
return
new
Map
(
Array
.
from
(
map
,
(
[
k
,
v
]
)
=>
[
k
,
regroup
(
v
,
i
+
1
)
]
)
)
;
}
)
(
values
,
0
)
;
}
Insert cell
rollup
(
data
,
v
=>
v
.
length
,
d
=>
d
.
name
,
d
=>
d
.
date
)
Insert cell
rollup
(
data
,
v
=>
v
.
length
,
d
=>
d
.
name
)
Insert cell
rollup
(
data
,
v
=>
v
.
length
)
Insert cell
Insert cell
Insert cell
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