Databases Reference
In-Depth Information
10
9
8
7
6
5
4
3
2
1
0
5
10
15
20
25
30
price
($)
Figure 3.7
A histogram for
price
using singleton buckets—each bucket represents one price-value/
frequency pair.
25
20
15
10
5
0
1-10
11-20
21-30
price
($)
Figure 3.8
An equal-width histogram for
price
, where values are aggregated so that each bucket has a
uniform width of $10.
“How are the buckets determined and the attribute values partitioned?”
There are
several partitioning rules, including the following:
Equal-width
: In an equal-width histogram, the width of each bucket range is
uniform (e.g., the width of $10 for the buckets in Figure 3.8).
Equal-frequency
(or equal-depth): In an equal-frequency histogram, the buckets are
created so that, roughly, the frequency of each bucket is constant (i.e., each bucket
contains roughly the same number of contiguous data samples).
