
erf, erfc  -  error  function  and  complementary  error

function

Calling sequence:

erf(x)
erfc(x)

Parameter:

x  --   expression

Overloading:

all

Summary:

The error function is defined as

    erf(x) = 2/sqrt(PI) * int( exp(-t^2), t=0..x )

The complementary error function is defined as

    1 - erf(x)

At the moment, evaluation is only possible for real arguments. erf and erfc
return the function call with the evaluated argument when the argument
cannot be evaluated to a number. erfc is a function of the system kernel.

>>  erfc(-0.2);

      1.222702589

>>  erfc(2); float(%);

      erfc(2)

      0.4677734981e-2

