npm install compute-erferf
===
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> Computes the error function.
The error function is defined as
Installation
`` bash`
$ npm install compute-erf
For use in the browser, use browserify.
Usage
` javascript`
var erf = require( 'compute-erf' );
#### erf( x[, options] )
Evaluates the error function (element-wise). x may be either a number, an array, a typed array, or a matrix. Values may include NaN, +infinity, and -infinity.
` javascript
var matrix = require( 'dstructs-matrix' ),
data,
mat,
out,
i;
out = erf( -1 );
// returns -0.8427
out = erf( [ -10, -1, 0, 1, 10 ] );
// returns [ -1, -0.8427, 0, 0.8427, 1 ]
data = [ 0, 1, 2 ];
out = erf( data );
// returns [ 0, ~0.8427007, ~0.9953222 ]
data = new Int8Array( data );
out = erf( data );
// returns Float64Array( [ 0, ~0.8427007, ~0.9953222 ] )
data = new Float64Array( 6 );
for ( i = 0; i < 6; i++ ) {
data[ i ] = i / 2;
}
mat = matrix( data, [3,2], 'float64' );
/*
[ 0 0.5
1 1.5
2 2.5 ]
*/
out = erf( mat );
/*
[ 0 ~0.52
~0.84 ~0.97
~1 ~1 ]
*/
`
The function accepts the following options:
* __accessor__: accessor function for accessing array values.typed array
* __dtype__: output or matrix data type. Default: float64.boolean
* __copy__: indicating if the function should return a new data structure. Default: true.'.'
* __path__: deepget/deepset key path.
* __sep__: deepget/deepset key path separator. Default: .
For non-numeric arrays, provide an accessor function for accessing array values.
` javascript
var data = [
['beep', -10],
['boop', -1],
['bip', 0],
['bap', 1],
['baz', 10]
];
function getValue( d, i ) {
return d[ 1 ];
}
var out = erf( data, {
'accessor': getValue
});
// returns [ -1, -0.8427, 0, 0.8427, 1 ]
`
To deepset an object array, provide a key path and, optionally, a key path separator.
` javascript
var data = [
{'x':[0,-10]},
{'x':[1,-1]},
{'x':[2,0]},
{'x':[3,1]},
{'x':[4,10]}
];
var out = erf( data, 'x|1', '|' );
/*
[
{'x':[0,-1]},
{'x':[1,-0.8427]},
{'x':[2,0]},
{'x':[3,0.8427]},
{'x':[4,1]}
]
*/
var bool = ( data === out );
// returns true
`
By default, when provided a typed array or matrix, the output data structure is float64 in order to preserve precision. To specify a different data type, set the dtype option (see matrix for a list of acceptable data types).
` javascript
var data, out;
data = new Int8Array( [0, 1, 2] );
out = erf( data, {
'dtype': 'int32'
});
// returns Int32Array( [0,0,0] )
// Works for plain arrays, as well...
out = erf( [0, 1, 2], {
'dtype': 'uint8'
});
// returns Uint8Array( [0,0,0] )
`
By default, the function returns a new data structure. To mutate the input data structure (e.g., when input values can be discarded or when optimizing memory usage), set the copy option to false.
` javascript
var data,
bool,
mat,
out,
i;
var data = [ -10, -1, 0, 1, 10 ];
var out = erf( data, {
'copy': false
});
// returns [ -1, -0.8427, 0, 0.8427, 1 ]
bool = ( data === out );
// returns true
data = new Float64Array( 6 );
for ( i = 0; i < 6; i++ ) {
data[ i ] = i / 2;
}
mat = matrix( data, [3,2], 'float64' );
/*
[ 0 0.5
1 1.5
2 2.5 ]
*/
out = erf( mat, {
'copy': false
});
/*
[ 0 ~0.52
~0.84 ~0.97
~1 ~1 ]
*/
bool = ( mat === out );
// returns true
`
Notes
* If an element is __not__ a numeric value, the evaluated error function is NaN.
` javascript
var data, out;
out = erf( null );
// returns NaN
out = erf( true );
// returns NaN
out = erf( {'a':'b'} );
// returns NaN
out = erf( [ true, null, [] ] );
// returns [ NaN, NaN, NaN ]
function getValue( d, i ) {
return d.x;
}
data = [
{'x':true},
{'x':[]},
{'x':{}},
{'x':null}
];
out = erf( data, {
'accessor': getValue
});
// returns [ NaN, NaN, NaN, NaN ]
out = erf( data, {
'path': 'x'
});
/*
[
{'x':NaN},
{'x':NaN},
{'x':NaN,
{'x':NaN}
]
*/
`
* Be careful when providing a data structure which contains non-numeric elements and specifying an integer output data type, as NaN values are cast to 0.
` javascript`
var out = erf( [ true, null, [] ], {
'dtype': 'int8'
});
// returns Int8Array( [0,0,0] );
Examples
` javascript
var matrix = require( 'dstructs-matrix' ),
erf = require( 'compute-erf' );
var data,
mat,
out,
tmp,
i;
// Plain arrays...
data = new Array( 10 );
for ( i = 0; i < data.length; i++ ) {
data[ i ] = Math.random()*20 - 10;
}
out = erf( data );
// Object arrays (accessors)...
function getValue( d ) {
return d.x;
}
for ( i = 0; i < data.length; i++ ) {
data[ i ] = {
'x': data[ i ]
};
}
out = erf( data, {
'accessor': getValue
});
// Deep set arrays...
for ( i = 0; i < data.length; i++ ) {
data[ i ] = {
'x': [ i, data[ i ].x ]
};
}
out = erf( data, {
'path': 'x/1',
'sep': '/'
});
// Typed arrays...
data = new Int32Array( 10 );
for ( i = 0; i < data.length; i++ ) {
data[ i ] = Math.random() * 100;
}
tmp = erf( data );
out = '';
for ( i = 0; i < data.length; i++ ) {
out += tmp[ i ];
if ( i < data.length-1 ) {
out += ',';
}
}
// Matrices...
mat = matrix( data, [5,2], 'int32' );
out = erf( mat );
// Matrices (custom output data type)...
out = erf( mat, {
'dtype': 'uint8'
});
`
To run the example code from the top-level application directory,
` bash`
$ node ./examples/index.js
Tests
$3
Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:
` bash`
$ make test
All new feature development should have corresponding unit tests to validate correct functionality.
$3
This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:
` bash`
$ make test-cov
Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,
` bash``
$ make view-cov
---
License
Copyright
Copyright © 2014-2015. The Compute.io Authors.
[npm-image]: http://img.shields.io/npm/v/compute-erf.svg
[npm-url]: https://npmjs.org/package/compute-erf
[travis-image]: http://img.shields.io/travis/compute-io/erf/master.svg
[travis-url]: https://travis-ci.org/compute-io/erf
[coveralls-image]: https://img.shields.io/coveralls/compute-io/erf/master.svg
[coveralls-url]: https://coveralls.io/r/compute-io/erf?branch=master
[dependencies-image]: http://img.shields.io/david/compute-io/erf.svg
[dependencies-url]: https://david-dm.org/compute-io/erf
[dev-dependencies-image]: http://img.shields.io/david/dev/compute-io/erf.svg
[dev-dependencies-url]: https://david-dm.org/dev/compute-io/erf
[github-issues-image]: http://img.shields.io/github/issues/compute-io/erf.svg
[github-issues-url]: https://github.com/compute-io/erf/issues