###
Calling Sequence

Result = DERIVSIG(*
[X, Y, Sigx,] Sigy*
)

###
Arguments

####
X

The variable to differentiate with respect to. If omitted, unit spacing for Y (i.e., X*
i*
= *
i*
) is assumed.

####
Y

The variable to be differentiated. Omit if *
X*
is omitted.

####
Sigx

The standard deviation of *
X*
(either vector or constant). Use "0.0" if the abscissa is exact; omit if *
X*
is omitted.

####
Sigy

The standard deviation of *
Y*
. *
Sigy*
must be a vector if the other arguments are omitted, but may be either a vector or a constant if *
X*
, *
Y*
, and *
Sigx*
are supplied.