Deletes every Nth sample for FIR downsampling.
DOWNSAMPLE(series, n, offset)
|
series |
- |
Any series, multi-series table, or expression resulting in a series or table. |
|
n |
- |
An integer factor by which to decimate the series. Deletes N-1 samples between each sample, decreasing the sample rate by a factor of N. Defaults to 1, no rate change. |
|
offset |
- |
Optional. An integer, the starting offset for the decimation. Defaults to 0, start decimation after the first sample. |
A series, the decimated series.
W1: 1..5
W2: downsample(W1, 2)
W2 == {1, 3, 5}
rate(w1) == 1
rate(w2) == 0.5
Reduces the series in W1 by a factor of 2 by keeping every other point.
W3: 1..5
W4: downsample(W3, 3)
W4 == {1, 4}
rate(w3) == 1
rate(w4) == 1/3
Reduces the series in W3 by a factor of 3 by keeping every third point.
W1: 1..5
W2: downsample(W1, 3, 1)
W2 == {2, 5}
rate(w3) == 1
rate(w4) == 1/3
Reduces the series in Window 1 by a factor of 3 by keeping every third point starting at the second point.
DOWNSAMPLE decreases the sample RATE of the input series by a factor of N by removing
A downsampled series can be decimated by filtering the result with a low pass filter with a cut off frequency of (Fs/2) / N where Fs is the original sample rate. The band limited frequency content of the original series is preserved.
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.