Syntax: @ERF(L[, U])
L = Lower bound for integrating ERF, L>=0
U = (Optional) Upper bound for integrating ERF
@ERF returns the error function integrated between L and U. The function is given by:
If U is omitted, @ERF integrates between 0 and L:
Examples:
@ERF(1) = 0.8427
@ERF(0.35) = 0.3794
@ERF(0.35, 0.89) = 0.4125