Value must be a scalor or a matrix

I'm not really sure what is wrong with my document.   If I simply evaluate the function ZL() I get a vector output (or what I'd call a vector - matrix with one column).  When I take the same function and assign to a variable I get the error screen captured below.  

Is there a way to explicitly define a variable to be a vector or matrix?   Or, is that not the problem?  I've attached the Mathcad Prime document.

EDIT:  Looks like the issue might be because I'm using a range variable (see link below).   So, how do I convert a range variable to a matrix/vector variable?

https://support.ptc.com/help/mathcad/r8.0/en/index.html#page/PTC_Mathcad_Help/range_variables.html