Calculates the derivative of a series
using a
RDERIV(series, method)
series 
 
An interval or XY series, the series to differentiate.  
method 
 
Optional. An integer, the last point calculation method. Defaults to 0.

A series or table.
W1: 2..5
W2: rderiv(W1)
W3: rderiv(W1, 1)
W2 == {1, 1, 1, 5}
W3 == {1, 1, 1, 1}
W2 and W3 compute the right derivative of the series {2, 3, 4, 5}. The results are identical except for the first point.
W1: 2..5;setdeltax(1/10)
W2: rderiv(W1)
W3: rderiv(W1, 1)
W2 == {10, 10, 10, 50}
W3 == {10, 10, 10, 10}
Same as above except the results are multiplied by the inverse of the DELTAX.
RDERIV computes the 2 point derivative of series s as follows:
For method == 0 (default), the data is assumed to be zero beyond the last sample, thus for a series of N points, the derivative at the last point is computed as:
For method == 1,
The end point treatment of method 1 generally results in a smaller end point discontinuity when the end point of the input data is not near zero.
See LDERIV to compute the 2 point left derivative.
See DERIV to compute the derivative using a quadratic polynomial.
See DIFF to compute the series differences.