polyeig gives different eigen values for the same matrices.

I am trying to find eigen value for a system with the Global mass, stiffness and damping matrix. There are two sets of matrices with one set name as:

GLK - Global stiffness matrix

GLC - Global damping matrix

GLM - Global mass matrix

and the other set as

glk - Global stiffness matrix

gld - Global damping matrix

glm - Global mass matrix.

In spite of the fact that both set of matrices are exactly the same, polyeig returns different eigen values.

In the matlab file that I have attached a and b are:

a = polyeig(GLK,GLC,GLM);
b = polyeig(glk,gld,glm);

Answer 1

[Walter Roberson]

In spite of the fact that both set of matrices are exactly the same

But they are not.

>> isequal(GLC,gld)

ans =

  logical

   0
>> max(max(GLC-gld))

ans =

         0.224105817267403

>> min(min(GLC-gld))

ans =

        -0.224105817267403

I find it odd that for the two that are exactly the same, that the names are upper/lower case of each other, and that for the ones that differ, the names differ (GLC vs gld) and I have to wonder if you have accidently used the wrong matrix.