Y = downsample(X, n)
Y = downsample(X, n, phase)
Y = downsample(X, n, phase, dim)
| Parameter | Description |
|---|---|
| X | input sequence. Vector or matrix. If X is a matrix, columns are processed independently by default. |
| n | positive integer downsampling factor (n > 0). |
| phase | optional integer in the range 0..n-1 (default 0). The output starts at X(phase+1) and then takes every n-th sample. |
| dim | optional dimension along which to downsample. If omitted, downsampling is applied to columns for 2-D inputs. |
| Parameter | Description |
|---|---|
| Y | downsampled result: elements of X taken every n samples starting at index (phase + 1) along the specified dimension. |
The downsample function returns every n-th sample of the input sequence X, beginning at sample index (phase + 1). For example, downsample(X, 2) returns the odd-indexed samples of X (1,3,5,...). If X is a matrix, the operation is applied column-wise by default unless a dimension is provided.
No anti-aliasing filtering is performed; if you need to reduce high-frequency content before decimation, consider using decimate or applying a low-pass filter first.
% Downsample a vector by 2
X = 1:10;
Y = downsample(X, 2);
% Y is [1 3 5 7 9]
% Downsample with phase = 1 (start at second element)
Y2 = downsample(X, 3, 1);
% Y2 is [2 5 8]
% Downsample columns of a matrix by 2
A = reshape(1:12, 4, 3);
B = downsample(A, 2);| Version | Description |
|---|---|
| 1.15.0 | initial version |