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FIRST_DIFF

FIRST_DIFF

Name


FIRST_DIFF

Purpose


This function returns the first difference vector of the input.

Category


Time Series Analysis

Calling Sequence


Result = FIRST_DIFF( Vect )

Inputs


Vect: A vector of type integer or floating point.

Keyword Parameters


BACKWARD: Forces calculation of the backward difference. This
is the default.
FORWARD: Forces calculation of the forward difference. The
default is the backward difference.
CENTRED: Forces calculation of the centred difference. The
defalut is the backward difference.

Outputs


Result: Returns the first difference of the input vector.

Procedure


The function calculates the first difference of the values in
the input vector. Note that it cycles around and includes the
difference between the first and last elements.

Example


Define a vector.
x = [1,2,3]
Calculate the forward first differenc of x.
result = first_diff( x )

Modification History


  Written by: Daithi A. Stone, 2000-06-27.
Modified: Daithi A. Stone, 2000-07-06 (removed
LENGTH.pro).
Modified: Daithi A. Stone, 2000-07-10 (removed for loops).



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