How do I remove complex values from an array of eigenvalues?

[amca01]

I'm using the math.eigs function to compute all roots of a polynomial, with the eigenvalues of the companion matrix. However, I am only interested in real roots, and some values returned are complex. I can see all the roots with

 var evs = math.eigs(A, {eigenvectors: false, precision: 1e-6}).values;
 console.log(math.typeOf(evs));
 console.log(math.count(evs));
 console.log(math.size(evs));
 console.log(math.format(evs,6));

but I can't find out how to isolate individual values, or to remove the complex values. This, for example:

console.log(math.format(evs[0],6));

returns an error. (So does math.size above.) So I have two questions: (1) how do I access individual eigenvalues, and (2) is there a built-in way of determining if a number is real or complex? (In my case, I could simply ask if the imaginary part of a value was less than the precision, of course.) In any case, I need to remove the complex values, leaving only reals.

Thank you!

[josdejong]

The returned values is either an Array or a Matrix (depending on whether the input was an Array or Matrix). Getting a value out of an Array goes like values[0], and if the result is a Matrix you can do values.get([0]). You can look up the docs for more information on how to work with arrays and matrices.

To filter out complex values you can use functions like math.filter and math.isComplex.