DSP Blockset

Mean

Find the mean value of an input or sequence of inputs.

Library

Statistics

Description

The Mean block computes the mean of each column in the input, or tracks the mean values in a sequence of inputs over a period of time. The Running mean parameter selects between basic operation and running operation.

Basic Operation

When the Running mean check box is not selected, the block computes the mean of each column of M-by-N input matrix u independently at each sample time.

y = mean(u)          % Equivalent MATLAB code

For convenience, length-M 1-D vector inputs and sample-based length-M row vector inputs are both treated as M-by-1 column vectors.

The output at each sample time, y, is a 1-by-N vector containing the mean value for each column in u. The mean of a complex input is computed independently for the real and imaginary components, as shown below.

The frame status of the output is the same as that of the input.

Running Operation

When the Running mean check box is selected, the block tracks the mean value of each channel in a time-sequence of M-by-N inputs. For sample-based inputs, the output is a sample-based M-by-N matrix with each element yij containing the mean value of element uij over all inputs since the last reset. For frame-based inputs, the output is a frame-based M-by-N matrix with each element yij containing the mean value of the jth column over all inputs since the last reset, up to and including element uij of the current input.

If the Reset port parameter is set to Non-zero sample, the optional Rst port is enabled and the block resets the running mean when the scalar input at the Rst port is nonzero. (The Rst port can be disabled by setting the Reset port parameter to None.) For sample-based inputs, the running mean for each channel is initialized to the value in the corresponding channel of the current input. For frame-based inputs, the running mean for each channel is initialized to the earliest value in each channel of the current input.

As in basic operation, length-M 1-D vector inputs and sample-based length-M row vector inputs are both treated as M-by-1 column vectors.

Example

The Mean block in the model below calculates the running mean of a frame-based 3-by-2 (two-channel) matrix input, u. The running mean is reset at t=2 by an impulse to the block's Rst port.

The Mean block has the following settings:

• Running mean =
• Reset port = Non-zero sample

The Signal From Workspace block has the following settings:

• Signal = u
• Sample time = 1/3
• Samples per frame = 3

where

u = [6 1 3 -7 2 5 8 0 -1 -3 2 1;1 3 9 2 4 1 6 2 5 0 4 17]'

The Discrete Impulse block has the following settings:

• Delay (samples) = 2
• Sample time = 1
• Samples per frame = 1

The block's operation is shown in the figure below.

The statsdem demo illustrates the operation of several blocks from the Statistics library.

Dialog Box

Running mean

Enables running operation when selected.

Reset port

Enables the Rst input port when set to Non-zero sample, and disables the Rst input port when set to None.

See Also

Maximum	DSP Blockset
Median	DSP Blockset
Minimum	DSP Blockset
Standard Deviation	DSP Blockset
mean	MATLAB

Maximum

Median