Package Exports

ema-stream

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (ema-stream) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

ema-stream

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

Travis

example - module

numbers source

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);
})

output

3
10
18
etc

json source

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);
});

output

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

methods

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.