LinearVelocity

LinearVelocity - Compute instantaneous linear velocity.

 Compute linear velocity for a time-varying vector X.

  USAGE

    V = LinearVelocity(X,smooth)

    X              position <a href="matlab:help samples">samples</a>
    smooth         optional standard deviation for Gaussian kernel used for
                   differentiating, measured in number of samples
                   (default = no smoothing)

  SEE

    See also AngularVelocity.

0001 function V = LinearVelocity(X,smooth)
0002 
0003 %LinearVelocity - Compute instantaneous linear velocity.
0004 %
0005 % Compute linear velocity for a time-varying vector X.
0006 %
0007 %  USAGE
0008 %
0009 %    V = LinearVelocity(X,smooth)
0010 %
0011 %    X              position <a href="matlab:help samples">samples</a>
0012 %    smooth         optional standard deviation for Gaussian kernel used for
0013 %                   differentiating, measured in number of samples
0014 %                   (default = no smoothing)
0015 %
0016 %  SEE
0017 %
0018 %    See also AngularVelocity.
0019 
0020 % Copyright (C) 2004-2011 by Michaël Zugaro
0021 %
0022 % This program is free software; you can redistribute it and/or modify
0023 % it under the terms of the GNU General Public License as published by
0024 % the Free Software Foundation; either version 3 of the License, or
0025 % (at your option) any later version.
0026 
0027 if nargin < 1,
0028     error('Incorrect number of parameters (type ''help <a href="matlab:help LinearVelocity">LinearVelocity</a>'' for details).');
0029 end
0030 if nargin >= 2,
0031     if ~isdscalar(smooth,'>=0'),
0032         error('Incorrect smoothing stdev (type ''help <a href="matlab:help LinearVelocity">LinearVelocity</a>'' for details).');
0033     end
0034 else
0035     smooth = 0;
0036 end
0037 
0038 DX = Diff(X,'smooth',smooth);
0039 Y = DX(:,2:3).*DX(:,2:3);
0040 N = sqrt(Y(:,1)+Y(:,2));
0041 V = [X(:,1) N];