Returns a 1xN array of approximations to the derivatives at the points in the input data. To compute the derivative, the DIFF function fits a cubic spline to the input data and returns the derivatives of the approximating polynomials at each point.
The length of the INDEP array must be equal to the DEPEND array.
Format
DIFF (INDEP, DEPEND)
Arguments
INDEP | A 1xN array of independent data. These x values must be in ascending order, and the length of the array must be greater than or equal to 4. |
DEPEND | A 1xN array of dependent data on input independent data. |
Example
The following example illustrates the use of the DIFF function:
Function | DIFF(SERIES(0,1,5), {0,1,4,9,16}) |
Result | 0, 2.0, 4.0, 6.0, 8.0 |