compute-erfinv
v3.0.1
Published
Inverse error function.
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erfinv
The inverse error function is defined in terms of the Maclaurin series
where c_0 = 1
and
Installation
$ npm install compute-erfinv
For use in the browser, use browserify.
Usage
var erfinv = require( 'compute-erfinv' );
erfinv( x[, options] )
Evaluates the inverse error function. x
may be either a number
, an array
, a typed array
, or a matrix
. All numeric values must reside on the interval [-1,1]
.
var matrix = require( 'dstructs-matrix' ),
data,
mat,
out,
i;
out = erfinv( 0.5 );
// returns ~0.47694
out = erfinv( [ 0, 0.2, 0.5, 0.8, 1 ] );
// returns [ 0, 0.17914, 0.47694, 0.90619, +infinity ]
data = [ 0, 0.5, 1 ];
out = erfinv( data );
// returns [ 0, 0.47694, +infinity ]
data = new Float32Array( data );
out = erfinv( data );
// returns Float64Array( [ 0, 0.47694, +infinity ] )
data = new Float64Array( 4 );
for ( i = 0; i < 4; i++ ) {
data[ i ] = i / 2;
}
mat = matrix( data, [2,2], 'float64' );
/*
[ 0 0.25
0.5 0.75 ]
*/
out = erfinv( mat );
/*
[ 0 ~0.2253
~0.4769 ~0.8134 ]
*/
The function accepts the following options
:
- accessor: accessor
function
for accessingarray
values. - dtype: output
typed array
ormatrix
data type. Default:float64
. - copy:
boolean
indicating if thefunction
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.
var data = [
['beep', 0],
['boop', 0.2],
['bip', 0.5],
['bap', 0.8],
['baz', 1]
];
function getValue( d, i ) {
return d[ 1 ];
}
var out = erfinv( data, {
'accessor': getValue
});
// returns [ 0, 0.17914, 0.47694, 0.90619, +infinity ]
To deepset an object array
, provide a key path and, optionally, a key path separator.
var data = [
{'x':[0,0]},
{'x':[1,0.25]},
{'x':[2,0.5]},
{'x':[3,0.75]},
{'x':[4,1]}
];
var out = erfinv( data, 'x|1', '|' );
/*
[
{'x':[0,0]},
{'x':[1,0.2253]},
{'x':[2,0.4769]},
{'x':[3,0.8134]},
{'x':[4,+infinity]}
]
*/
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).
var data, out;
data = new float64Array( [0, 0.25, 0.5] );
out = erfinv( data, {
'dtype': 'int32'
});
// returns Int32Array( [0,0,0] )
// Works for plain arrays, as well...
out = erfinv( [0, 0.25, 0.5], {
'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
.
var data,
bool,
mat,
out,
i;
var data = [ 0, 0.2, 0.5, 0.8, 1 ];
var out = erfinv( data, {
'copy': false
});
// returns [ 0, 0.17914, 0.47694, 0.90619, +infinity ]
bool = ( data === out );
// returns true
data = new Float64Array( 4 );
for ( i = 0; i < 4; i++ ) {
data[ i ] = i / 4;
}
mat = matrix( data, [2,2], 'float64' );
/*
[ 0 0.25
0.5 0.75 ]
*/
out = erfinv( mat, {
'copy': false
});
/*
[ 0 ~0.2253
~0.4769 ~0.8134 ]
*/
bool = ( mat === out );
// returns true
Notes
If an element is not a numeric value, the evaluated inverse error function is
NaN
.var data, out; out = erfinv( null ); // returns NaN out = erfinv( true ); // returns NaN out = erfinv( {'a':'b'} ); // returns NaN out = erfinv( [ true, null, [] ] ); // returns [ NaN, NaN, NaN ] function getValue( d, i ) { return d.x; } data = [ {'x':true}, {'x':[]}, {'x':{}}, {'x':null} ]; out = erfinv( data, { 'accessor': getValue }); // returns [ NaN, NaN, NaN, NaN ] out = erfinv( 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, asNaN
values are cast to0
.var out = erfinv( [ true, null, [] ], { 'dtype': 'int8' }); // returns Int8Array( [0,0,0] );
Examples
var matrix = require( 'dstructs-matrix' ),
erfinv = require( 'compute-erfinv' );
var data,
mat,
out,
tmp,
i;
// Plain arrays...
data = new Array( 100 );
for ( i = 0; i < data.length; i++ ) {
data[ i ] = ( Math.random() - 0.5 ) * 2;
}
out = erfinv( data );
// Object arrays (accessors)...
function getValue( d ) {
return d.x;
}
for ( i = 0; i < data.length; i++ ) {
data[ i ] = {
'x': data[ i ]
};
}
out = erfinv( data, {
'accessor': getValue
});
// Deep set arrays...
for ( i = 0; i < data.length; i++ ) {
data[ i ] = {
'x': [ i, data[ i ].x ]
};
}
out = erfinv( data, {
'path': 'x/1',
'sep': '/'
});
// Typed arrays...
data = new Int32Array( 10 );
for ( i = 0; i < data.length; i++ ) {
data[ i ] = ( Math.random() - 0.5 ) * 2;
}
tmp = erfinv( 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 = erfinv( mat );
// Matrices (custom output data type)...
out = erfinv( mat, {
'dtype': 'uint8'
});
To run the example code from the top-level application directory,
$ node ./examples/index.js
Tests
Unit
Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:
$ make test
All new feature development should have corresponding unit tests to validate correct functionality.
Test Coverage
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:
$ make test-cov
Istanbul creates a ./reports/coverage
directory. To access an HTML version of the report,
$ make view-cov
License
Copyright
Copyright © 2014-2015. The Compute.io Authors.