# v_rotmr2qr

## PURPOSE

V_ROTMR2QR converts a matrix of real quaternion matrices to quaternion vectors

## SYNOPSIS

function qr=v_rotmr2qr(mr)

## DESCRIPTION

    V_ROTMR2QR converts a matrix of real quaternion matrices to quaternion vectors
     Inputs:

         MR(4m,4n,...)   mxn matrix of real quaternion matrices (each 4x4)

     Outputs:

         QR(4m,n,...)   mxn matrix of real quaternion vectors (each 4x1)

     In matrix form, quaternions can be multiplied and added using normal matrix
     arithmetic. Each element of an mxn matrix of quaternions is itself a 4x4 block
     so the total dimension of MR is 4m x 4n.

## CROSS-REFERENCE INFORMATION

This function calls:

- v_rotqr2ro ROTQR2RO converts a real quaternion to a 3x3 rotation matrix

This function is called by:

## SOURCE CODE

    0001 function qr=v_rotmr2qr(mr)
    0002 %V_ROTMR2QR converts a matrix of real quaternion matrices to quaternion vectors
    0003 % Inputs:
    0004 %
    0005 %     MR(4m,4n,...)   mxn matrix of real quaternion matrices (each 4x4)
    0006 %
    0007 % Outputs:
    0008 %
    0009 %     QR(4m,n,...)   mxn matrix of real quaternion vectors (each 4x1)
    0010 %
    0011 % In matrix form, quaternions can be multiplied and added using normal matrix
    0012 % arithmetic. Each element of an mxn matrix of quaternions is itself a 4x4 block
    0013 % so the total dimension of MR is 4m x 4n.
    0014
    0015 %
    0016 %      Copyright (C) Mike Brookes 2000-2018
    0017 %      Version: $Id: v_rotmr2qr.m 10865 2018-09-21 17:22:45Z dmb $
    0018 %
    0019 %   VOICEBOX is a MATLAB toolbox for speech processing.
    0020 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
    0021 %
    0022 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    0023 %   This program is free software; you can redistribute it and/or modify
    0024 %   it under the terms of the GNU Lesser General Public License as published by
    0025 %   the Free Software Foundation; either version 3 of the License, or
    0026 %   (at your option) any later version.
    0027 %
    0028 %   This program is distributed in the hope that it will be useful,
    0029 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
    0030 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    0031 %   GNU Lesser General Public License for more details.
    0032 %
    0033 %   You can obtain a copy of the GNU Lesser General Public License from
    0034 %   https://www.gnu.org/licenses/ .
    0035 %
    0036 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    0037 s=size(mr);
    0038 s(2)=s(2)/4;
    0039 mr=reshape(mr,s(1),[]);
    0040 qr=reshape(mr(:,1:4:end),s);
    0041 if ~nargout
    0042     qr=qr(1:4); % select the first element
    0043     v_rotqr2ro(qr(:)); % plot a rotated cube
    0044 end