Calculates the derivative of a series or series expression using a
LDERIV(series, method)
series 
 
An interval or XY series, the series to differentiate. 

method 
 
Optional. An integer, the first point calculation method. Defaults to 0.

A series or table.
W1: 2..5
W2: lderiv(W1)
W3: lderiv(W1, 1)
W2 == {2, 1, 1, 1}
W3 == {1, 1, 1, 1}
W2 and W3 compute the left derivative of the series {2, 3, 4, 5}. The results are identical except for the first point.
W1: 2..5;setdeltax(1/10)
W2: lderiv(W1)
W3: lderiv(W1, 1)
W2 == {20, 10, 10, 10}
W3 == {10, 10, 10, 10}
Same as above except the results are multiplied by the inverse of the DELTAX.
LDERIV computes the 2 point derivative of series s as follows:
For method == 0 (default), the data is assumed to be zero before the first sample, thus the derivative at the first point is computed as:
For method == 1,
The method 1 first point treatment generally results in a smaller start point discontinuity when the start point of the input data is not near zero.
See RDERIV to compute the 2 point right derivative.
See DERIV to compute the derivative using a quadratic polynomial.
See DIFF to compute the series difference.