# Function erf Compute the erf function of a value using a rational Chebyshev approximations for different intervals of x. This is a translation of W. J. Cody's Fortran implementation from 1987 ( https://www.netlib.org/specfun/erf ). See the AMS publication "Rational Chebyshev Approximations for the Error Function" by W. J. Cody for an explanation of this process. For matrices, the function is evaluated element wise. ## Syntax ```js math.erf(x) ``` ### Parameters Parameter | Type | Description --------- | ---- | ----------- `x` | number | Array | Matrix | A real number ### Returns Type | Description ---- | ----------- number | Array | Matrix | The erf of `x` ### Throws Type | Description ---- | ----------- ## Examples ```js math.erf(0.2) // returns 0.22270258921047847 math.erf(-0.5) // returns -0.5204998778130465 math.erf(4) // returns 0.9999999845827421 ```