NAME:spl_fstdrv
PURPOSE: SPL_FSTDRV returns the values of the first derivative of
the interpolating function at the points X2i. it is a double
precision array.
Given the arrays X and Y, which tabulate a function (with the X[i]
AND Y[i] in ascending order), and given an input value X2, the
SPL_INCR function returns an interpolated value for the given values
of X2. The interpolation method is based on cubic spline, corrected
in a way that interpolated value are also in ascending order
CATEGORY:
CALLING SEQUENCE: y2 = spl_fstdrv(x, y, yscd, x2)
INPUTS:
x: An n-element (at least 2) input vector that specifies the
tabulate points in ascending order.
y: f(x) = y. An n-element input vector that specifies the values
of the tabulated function F(Xi) corresponding to Xi.
yscd: The output from SPL_INIT for the specified X and Y.
x2: The input values for which the first derivative values are
desired. X can be scalar or an array of values.
KEYWORD PARAMETERS: none
OUTPUTS:
y2: f'(x2) = y2.
COMMON BLOCKS: none
SIDE EFFECTS: ?
RESTRICTIONS: ?
EXAMPLE:
MODIFICATION HISTORY: