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Bessel function of the second kind of order one


High performance, rigorous, and robust mathematical and statistical functions. Build advanced statistical models and machine learning libraries.

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Scatter plot with axis rug plots.

Data visualization

Plotting and graphics functionality for data visualization and exploratory data analysis. Analyze and understand your data.

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function indicator( v ) {
    return v[ 0 ];
var arr = [ 'beep', 'boop', 'foo', 'bar' ];

var out = groupBy( arr, indicator );
// returns { 'b': [ 'beep', 'boop', 'bar' ], 'f': [ 'foo' ] }
function predicate( key, value ) {
    return ( value > 1 );

var obj1 = {
    'a': 1,
    'b': 2,
    'c': 3

var obj2 = omitBy( obj1, predicate );
// returns { 'a': 1 }


Comprehensively tested utilities for application and library development. Functions to assert, group, filter, map, pluck, and transform your data both in browsers and on the server. Everything you would expect from a modern standard library.

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Comprehensive documentation and examples.


Consistent interfaces combined with extensive documentation, examples, tests, and benchmarks. High quality implementations so you can focus less on finding the right package and more on getting work done.

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Real-eval-print-loop displaying integrated help.


A read-eval-print-loop with integrated help and examples. Interactively manipulate data and prototype solutions with over 1500 built-in functions for mathematics, statistics, machine learning, streams, plotting, and more.

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Editor displaying a source file with annotations

Open Source

Designed from the ground-up to be forkable, hackable, and extensible. All code is licensed under a commercial friendly Apache license. Built with love by people from around the world.