# erfcinv
> [Inverse complementary error function][erfcinv].
The [inverse complementary error function][erfcinv] is defined as
where `erf^{-1}(z)` is the [inverse error function][@stdlib/math/base/special/erfinv].
## Usage
```javascript
var erfcinv = require( '@stdlib/math/base/special/erfcinv' );
```
#### erfcinv( x )
Evaluates the [inverse complementary error function][erfcinv].
```javascript
var y = erfcinv( 0.5 );
// returns ~0.4769
y = erfcinv( 0.8 );
// returns ~0.1791
y = erfcinv( 0.0 );
// returns Infinity
y = erfcinv( 2.0 );
// returns -Infinity
```
The domain of `x` is restricted to `[0,2]`. If `x` is outside this interval, the function returns `NaN`.
```javascript
var y = erfcinv( -3.14 );
// returns NaN
```
If provided `NaN`, the function returns `NaN`.
```javascript
var y = erfcinv( NaN );
// returns NaN
```
## Examples
```javascript
var linspace = require( '@stdlib/array/linspace' );
var erfcinv = require( '@stdlib/math/base/special/erfcinv' );
var x = linspace( 0.0, 2.0, 100 );
var y;
var i;
for ( i = 0; i < x.length; i++ ) {
y = erfcinv( x[ i ] );
console.log( 'x: %d, erfcinv(x): %d', x[ i ], y );
}
```
[erfcinv]: https://en.wikipedia.org/wiki/Error_function#Inverse_functions
[@stdlib/math/base/special/erfinv]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/erfinv
