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# matrixlincomb

## PURPOSE Linear combination function for tangent vectors represented as matrices.

## SYNOPSIS function v = matrixlincomb(x, a1, d1, a2, d2) %#ok

## DESCRIPTION ``` Linear combination function for tangent vectors represented as matrices.

function v = lincomb(x, a1, d1)
function v = lincomb(x, a1, d1, a2, d2)

Given a point x, two tangent vectors d1 and d2 at x, and two real
coefficients a1 and a2, returns a tangent vector at x representing
a1*d1 + a2*d2, if d1 and d2 are represented as matrices (or more
generally as arrays in Matlab).

If a2 and d2 are omitted, the returned tangent vector is a1*d1.

The input x is actually unused.

This function is a helper to define manifolds in Manopt.```

## CROSS-REFERENCE INFORMATION This function calls:
This function is called by:

## SOURCE CODE ```0001 function v = matrixlincomb(x, a1, d1, a2, d2) %#ok<INUSL>
0002 % Linear combination function for tangent vectors represented as matrices.
0003 %
0004 % function v = lincomb(x, a1, d1)
0005 % function v = lincomb(x, a1, d1, a2, d2)
0006 %
0007 % Given a point x, two tangent vectors d1 and d2 at x, and two real
0008 % coefficients a1 and a2, returns a tangent vector at x representing
0009 % a1*d1 + a2*d2, if d1 and d2 are represented as matrices (or more
0010 % generally as arrays in Matlab).
0011 %
0012 % If a2 and d2 are omitted, the returned tangent vector is a1*d1.
0013 %
0014 % The input x is actually unused.
0015 %
0016 % This function is a helper to define manifolds in Manopt.
0017
0018 % This file is part of Manopt: www.manopt.org.
0019 % Original author: Nicolas Boumal, July 2, 2015.
0020 % Contributors:
0021 % Change log:
0022
0023     if nargin == 3
0024         v = a1*d1;
0025     elseif nargin == 5
0026         v = a1*d1 + a2*d2;
0027     else
0028         error('matrixlincomb takes either 3 or 5 inputs.');
0029     end
0030
0031 end```

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