ema-stream
==========

Exponential moving average from a stream. Module and command line.

!Travis

example - module
================

numbers source

``js
var emaStream = require('ema-stream');

var ema = emaStream();

var count = 0;
function source () {
var r = count++;
ema.write(r.toString() + '\n');
}

setInterval(source, 100);

ema.on('readable', function () {
ema.pipe(process.stdout);
})
`

$3

`
3
10
18
etc
`

json source

`javascript
var emaStream = require('ema-stream');

var ema = emaStream({
pluck: ['key1', 'key2']
});

var count = 0;
function source () {
var obj = {
key1: count++,
key2: Math.random() * 500
};

ema.write(JSON.stringify(obj) + '\n');
}

setInterval(source, 100);

ema.on('readable', function () {
ema.pipe(process.stdout);
});
`

$3

`
{"key1":3,"key2":232}
{"key1":10,"key2":245}
{"key1":18,"key2":210}
etc.
`

methods

` js
var emaStream = require('ema-stream');
`

var ema = emaStream(opts)

Create a new stream instance ema with options opts:

* opts.window: 60000 - Length of window in ms.
* opts.pluck: null - Keys to pluck from incoming JSON. If unspecified,
incoming chunks is assumed to be numbers.
* opts.integers: true - Whether to round output.
* opts.refreshEvery: 1000 - How often to emit current average in ms.
* opts.emitFirstValue: false - Whether to emit on the first value or wait
until the first window has passed to emit the first time.

example - command line
======================

numbers source

`
$ counter
0
1
2
3
^C

$ counter | ema-stream
3 # Output is refreshed every second. 3, 10, 19, 28, etc.

`


json source

`
$ tail -f logfile.log
{"type":"request","statusCode":200,"wallTime":27,"dbConnections":40}
{"type":"request","statusCode":200,"wallTime":45,"dbConnections":42}
{"type":"request","statusCode":200,"wallTime":207,"dbConnections":48}
{"type":"request","statusCode":200,"wallTime":205,"dbConnections":50}
^C

Pluck only the keys we're interested in.


$ tail -f logfile.log | ema-stream --pluck wallTime,dbConnections
{"wallTime":62,"dbConnections":42} # Ouput is refreshed every second.
`

arguments

`
$ ema-stream \
--window 60000 # Window to calculcate moving average from in ms.
--integers true # Whether to round output.
--refreshEvery 1000 # How often to refresh current average in ms.
--pluck # Comma-separated list of keys to pluck from incoming JSON. If
unspecified, input is assumed to be numbers.
--emitFirstValue false # Whether to emit on the first value or wait
until the first window has passed to emit the first time.
``