movmean (for MATLAB older than R2016a).m

function u = movmean(v, varargin)
    %% Moving Mean
    %  This function is provided for backwards compatibility. It does the same
    %  job as the builtin function, movmean, which was introduced in MATLAB
    %  R2016a. It can be safely deleted on newer MATLAB.
    %
    %  u = movmean(v) computes the simple moving average of the vector v using
    %  sample width = 1.
    %
    %  u = movmean(v,w) computes the simple moving average of the vector v
    %  using sample width = w.
    %
    % Tested on:
    %  - MATLAB R2013b
    %  - MATLAB R2015b
    %
    % Copyright: Herianto Lim
    % https://heriantolim.com/
    % First created: 22/03/2013
    % Last modified: 20/10/2016

    %% Input Validation and Parsing
    assert(isvector(v) && isreal(v), ...
        'Input to the sample vector must be a real vector.');

    if isempty(varargin)
        w = 1;
    elseif isscalar(varargin{1}) && isreal(varargin{1}) && varargin{1} >= 0
        w = varargin{1};
    else
        error('Input to the sample width must be a positive real scalar.');
    end

    %% Simple Moving Average
    u = v;

    if w == 0
        return
    end

    n = numel(v);
    w = ceil(w / 2);

    for i = 2:w
        u(i) = mean(v(1:2 * i - 1));
        u(n - i + 1) = mean(v(n - 2 * i + 2:n));
    end

    n1 = 1 + w;
    n2 = n - w;

    for i = n1:n2
        u(i) = mean(v(i - w:i + w));
    end

end