downsample

Decrease sample rate by integer factor

Syntax

y = downsample(x,n)

y = downsample(x,n,phase)

Description

y = downsample(x,n) decreases the sample rate of x by keeping the first sample and then every nth sample after the first. If x is a matrix, the function treats each column as a separate sequence.

y = downsample(x,n,phase) specifies the number of samples by which to offset the downsampled sequence.

Examples

Decrease Sample Rates

Decrease the sample rate of a sequence by a factor of 3.

x = [1 2 3 4 5 6 7 8 9 10];
y = downsample(x,3)

y = 1×4

     1     4     7    10

Decrease the sample rate of the sequence by a factor of 3 and add a phase offset of 2.

y = downsample(x,3,2)

y = 1×3

     3     6     9

Decrease the sample rate of a matrix by a factor of 3.

x = [1  2  3;
     4  5  6;
     7  8  9;
    10 11 12];
y = downsample(x,3)

y = 2×3

     1     2     3
    10    11    12

Input Arguments

x — Input array

vector | matrix

Input array, specified as a vector or matrix. If x is a matrix, the function treats the columns as independent channels.

Example: cos(pi/4*(0:159)) + randn(1,160) specifies a sinusoid embedded in white Gaussian noise.

Example: cos(pi./[4;2]*(0:159))' + randn(160,2) specifies a two-channel noisy sinusoid.

n — Downsampling factor

positive integer

Downsampling factor, specified as a positive integer.

Data Types: single | double

phase — Offset

0 (default) | positive integer

Offset, specified as a positive integer from 0 to n – 1.

Data Types: single | double

Output Arguments

y — Downsampled array

vector | matrix

Downsampled array, returned as a vector or matrix.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

This function fully supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced before R2006a

R2024a: downsample supports GPU code generation

The downsample function supports code generation for graphical processing units (GPUs). You must have MATLAB^® Coder™ and GPU Coder™ to generate CUDA^® code.