Eig() matlab coder output

I have used the eig() function in matlab and obtained the V(Eigen vector) and D(eigen value).

Matlab output

0.491577650531798	-0.495336899750405	-0.716235135443169
0.503488034360681	-0.509405143984653	0.697858294023645
-0.710528826124074	-0.703667361064609	-0.00101598184714255

after using the matlab coder to convert this function to C, I'm getting a different eigen vector and value as the output. There is a change of sign.

C code array output - Comes in real and imaginary for which a workaround was found.

V = {-0.716235135443169, 0.697858294023645, -0.00101598184714255, 0.495336899750405, 0.509405143984653, 0.703667361064609, -0.491577650531798, -0.503488034360681, 0.710528826124074}
D = {0, 0, 81386639.3671520, 0, 256256.510446245, 0, 322.189392401933, 0, 0};

Is there any solution for this ? the output in C code seems to change the polarity randomly for different data.

Answer 1

[Walter Roberson]

eigenvectors are not unique; if V is an eigenvector of the matrix, then c*V is also an eigenvector of the matrix, where c is a non-zero scalar. In particular, if V is an eigenvector of the matrix, then -V is an eigenvector of the matrix.

It is common for people to normalize by taking the negative of the vector if the first non-zero element in the vector is negative.