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https://github.com/tolitius/multim
oh.. these tasty guava multi maps
https://github.com/tolitius/multim
clojure guava timeseries
Last synced: 3 months ago
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oh.. these tasty guava multi maps
- Host: GitHub
- URL: https://github.com/tolitius/multim
- Owner: tolitius
- License: epl-1.0
- Created: 2015-12-11T01:55:27.000Z (about 9 years ago)
- Default Branch: master
- Last Pushed: 2022-02-22T17:08:17.000Z (almost 3 years ago)
- Last Synced: 2024-06-09T16:34:32.691Z (8 months ago)
- Topics: clojure, guava, timeseries
- Language: Clojure
- Size: 11.7 KB
- Stars: 25
- Watchers: 2
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# multim
where a lonely key meets multiple values
[](http://clojars.org/tolitius/multim)
- [Why](#why)
- [Time Series](#time-series)
- [Multi Mode](#multi-mode)
- [Time Slicing](#time-slicing)
- [View with a View](#view-with-a-view)
- [License](#license)
## Why
They come handy. Sometimes. And at those times it's good to have them.
## Time Series
Let's say we have events streaming in in a form of `{timestamp {ticker event-id}}`:
```clojure
(def events [
[1449088877203 {:ticker :GOOG :event-id 1}]
[1449088876590 {:ticker :AAPL :event-id 2}]
[1449088877601 {:ticker :MSFT :event-id 3}]
[1449088877203 {:ticker :TSLA :event-id 4}]
[1449088875914 {:ticker :NFLX :event-id 5}]
[1449088870005 {:ticker :FB :event-id 6}] ])
```
* we'd like to keep them in a map.
* we'd also like to keep them _sorted_ by time (i.e. timestamp)
_notice_ that Tesla and Google have _the same timestamp_ (i.e. same key value).
## Multi Mode
As events come in they can be added into something like a [TreeMultimap](http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/TreeMultimap.html)
which is both: sorted and multimap.
```clojure
;; syntax: (tree-multimap [key-comparator] [value-comparator])
user=> (tree-multimap <)
#object[com.google.common.collect.TreeMultimap 0x1fabbda8 "{}"]
```
a map with no data is interesting, but not as much as a map with the data:
```clojure
user=> (def mm (into-multi
(tree-multimap <) events))
#object[com.google.common.collect.TreeMultimap 0x688a6108
"{1449088877601=[{:ticker :MSFT, :event-id 3}],
1449088877203=[{:ticker :GOOG, :event-id 1}, {:ticker :TSLA, :event-id 4}],
1449088876590=[{:ticker :AAPL, :event-id 2}],
1449088875914=[{:ticker :NFLX, :event-id 5}],
1449088870005=[{:ticker :FB, :event-id 6}]}"]
```
_notice_ how it groupped values for the `1449088877203` timestamp.
### Time Slicing
Since the map is sorted, it should be quite simple to find all the entries before or after certain time.
##### before
```clojure
user=> (to mm 1449088876592)
{1449088870005 #{{:ticker :FB, :event-id 6}},
1449088875914 #{{:ticker :NFLX, :event-id 5}},
1449088876590 #{{:ticker :AAPL, :event-id 2}}}
```
##### after
```clojure
user=> (from mm 1449088876592)
{1449088877203 #{{:ticker :GOOG, :event-id 1} {:ticker :TSLA, :event-id 4}},
1449088877601 #{{:ticker :MSFT, :event-id 3}}}
```
### View with a View
While `TreeMultimap` has all the chops, it is mutable, hence it is better to create a navigatable view based on the same `tree-multimap`:
```clojure
user=> (def view (into-view
(tree-multimap <) events))
#'user/view
user=> (type view)
com.google.common.collect.AbstractMapBasedMultimap$NavigableAsMap
```
it would of course be boring if this view type was not extended with a `Sliceable` protocol (as the `TreeMultimap` above):
```clojure
(defprotocol Sliceable
(from [this k])
(to [this k]))
```
so it does extend it as well:
##### before
```clojure
user=> (to view 1449088876592)
{1449088870005 #{{:ticker :FB, :event-id 6}},
1449088875914 #{{:ticker :NFLX, :event-id 5}},
1449088876590 #{{:ticker :AAPL, :event-id 2}}}
```
##### after
```clojure
user=> (from view 1449088876592)
{1449088877203 #{{:ticker :GOOG, :event-id 1} {:ticker :TSLA, :event-id 4}},
1449088877601 #{{:ticker :MSFT, :event-id 3}}}
```
## License
Copyright © 2022 tolitius
Distributed under the Eclipse Public License either version 1.0 or (at
your option) any later version.