vectorization - I need to change an array into vector in Prime 10

Terry already pointed you to the missing assignment.

But the first, simpler version of "vec" you show in your picture should work equally well!

Stuarts version has the benefit that it also unravels recursively nested vectors. But thats not necessary when you just want to turn a range into a vector. You also should not keep both versions of "vec" with the same name in your sheet. The call of "vec" in the "stack" function of the second "vec" variant would call the first variant and not itself as it should be. Thats the reason I renamed Stuarts function to "vec2" in the picture below which is just here to demonstrate what Stuarts function is capable of:

The simple "vec" is only good for turning a range into a vector.

Stuarts extended version will also deal with nested matrices.

It will not deal with matrices containing ranges, though 😉 😈

Dealing with this moloch, too, would make it necessary to add Stuarts "IsRange" function alongside the "IsArray".