topic Re: Indirect assignment of empty matrix in SAS/IML Software and Matrix Computations

Indirect assignment of empty matrix

IanWakeling — Sat, 21 Mar 2020 16:22:42 GMT

I was surprised recently to get a "Matrix has not been set to a value" error when attempting to assign an empty matrix using VALSET. If the syntax

x = {};

is acceptable, should it not be possible to do the same thing indirectly? For example,

call valset('x', {});

will generate the error referred to above. My actual code is more complex, where the 2nd argument to VALSET is a function that might occasionally return an empty matrix, so I have simplified things above to illustrate the point. I am using SAS/IML 15.1.

Re: Indirect assignment of empty matrix

Rick_SAS — Sat, 21 Mar 2020 17:39:07 GMT

You are correct. I do not have a workaround when the name of the symbol is not known until run time, since the FREE statement requires a symbol name, not a character string.

My only suggestion is to ask whether the function can return a missing value instead of an empty matrix. In my work, I often use a missing value to indicate an operation failed. It is easier to work with than an empty matrix.

Re: Indirect assignment of empty matrix

IanWakeling — Sat, 21 Mar 2020 17:57:00 GMT

Thanks for your reply Rick. I am still experimenting with Lists in IML, and I am using ListGetAllNames() which returns an empty matrix if there are no names associated with the list items. I am sure I will find a workaround.

Re: Indirect assignment of empty matrix

Ksharp — Sun, 22 Mar 2020 10:28:51 GMT

IsEmpty(x) could detect if x is empty .