Outliers Interquartile Range

Suggests outliers based on Interquartile Range method

The calculated bounds are
``
lower_bound = q25 - k * interquartile_range
upper_bound = q75 + k * interquartile_range
`

Any value outside these bounds is suggested as an outlier.


see https://en.wikipedia.org/wiki/Interquartile_range#Outliers for details

Installation

`
npm install @lgodard/outliers-interquartile-range
`

Example

`javascript
const outliersEngine = require('outliers-interquartile-range');

const options = {sorted: false, k: 1.5};

// array_values is 1-D array to be analyzed
const results = outliersEngine.getOutliers(array_values, options);
`

Documentation

|Option|type|default|description
|------ | ----------- |---|---|
|sorted|boolean|false|The submited data_array is already sorted, avoiding costly operation
|k |number |1.5| Interquartile range multiplier defining the threshold

Results

The getOutliers method returns an object with the following entries

|Entry|description
|------ | -----------|
|outliers| Object upper & lower outliers - see above
|stats |Object calculated values q25, q75 & iqr (interquartile range)
|parameters |Object the used parameters combining submitted options and defaults

The upper & lower objects contain

|Entry|description
|------ | -----------|
|threshold| number The limit for the value being suggested as outlier
|values | Array The suggested outlier values
|indexes |Array The indexes against submitted data_array suggested as outliers

`javascript

results = {
'outliers': {
'upper': {
'threshold': 64540.095,
'values': [ 193568.04, 128104.71, 235793.39, 157432.6 ],
'indexes': [ 11, 36, 43, 82]
},
'lower': {
'threshold': -36329.865,
'values': [],
'indexes': []
}
},
'parameters': {
'sorted': false,
'k': 1.5
},
'stats': {
'q25': 1496.37,
'q75': 26713.86,
'iqr': 25217.49
}
};

``

Acknowledgements

The main work (quartiles calculation) is done through the summary package.
Many thanks to the author.

License

MIT