If that hypothesis is rejected, one can use OLS . However, if the presence of a unit root is not rejected, then one should apply the difference operator to the series.
12.
A particularly basic form is the difference operator, which is convolution with the sequence (-1, 1, 0, \ ldots ), and is a discrete analog of the derivative.
13.
Moreover, higher-order derivative approximations can be computed in a straightforward manner ( and preserving scale-space properties ) by applying small support central difference operators to the discrete scale space representation.
14.
A classical example of a difference field is the field K = \ mathbb { C } ( x ) of rational functions with the difference operator \ sigma given by \ sigma ( f ( x ) ) = f ( x + 1 ).
15.
This can be checked directly on an annulus, using invariance of Sobolev spaces under dffeomorphisms and the fact that for the annulus the commutator of with a differential operator is obtained by applying the difference operator to the coefficients after having applied to the function:
16.
The training procedure for one stage is therefore to have many weak learners ( simple pixel difference operators ), train them as a group ( raise their weight if they give correct result ), but be mindful of having only a few active weak learners so the computation time remains low.
17.
When computing several derivatives in the N-jet simultaneously, discrete scale-space smoothing with the discrete analogue of the Gaussian kernel, or with a recursive filter approximation, followed by small support difference operators, may be both faster and more accurate than computing recursive approximations of each derivative operator.
18.
The term " indefinite summation " refers to the search for an inverse image of a given infinite sequence " s " of values for the forward difference operator, in other words for a sequence, called antidifference of " s ", whose finite differences are given by " s ".
19.
More examples of the use of the empty product in mathematics may be found in the binomial theorem ( which assumes and implies that " x " 0 = 1 for all " x " ), Stirling number, K�nig's theorem, binomial type, binomial series, difference operator and Pochhammer symbol.
20.
Just as differential equations have a discrete analog in difference equations with the forward difference operator replacing the derivative, so too there is the forward ratio operator " f " ( " x " + 1 ) / " f " ( " x " ) and recurrence relations can be formulated using this operator.
