DECIMATE

Purpose:

Linearly decimates (reduces) the sample rate and the number of points in a series by a factor n.

DECIMATE(series, n, start, blocksize)

series	-	A series or table.
n	-	An integer factor by which to decimate the series.
start	-	Optional. An integer specifying where to start the decimation.
blocksize	-	Optional. An integer, the number of points to preserve at every decimation interval. Defaults to 1.

A series.

W1: 1..5

W2: decimate(W1, 3)

Reduces the series in Window 1 by a factor of 3 by keeping every third point. W2 contains the series {1, 4}.

a = 1..20

decimate(a, 4, 10)

decimates the series a by a factor of 4, starting from the 10th point. Returns the series {10, 14, 18}.

W1: 1..10

W2: decimate(W1, 4, 1, 2)

Preserves two values at every 4th point. Returns the series {1, 2, 5, 6, 9, 10}.

Decimate is useful for extracting individual series from an interlaced source series:

W1: gsin(100,.01)

W2: gtri(100,.01)

W3: gnorm(100,.01)

W4: merge(W1, W2, W3)

W5: decimate(w4, 3, 1)

W6: decimate(W4, 3, 2)

W7: decimate(W4, 3, 3)

W5, W6 and W7 contain the original interlaced series of W1, W2 and W3.

The decimation factor automatically adjusts the sample rate (1/DELTAX) of the resulting series.

See DECILP to perform band limited decimation by means of low pass filtering.