I am having trouble with using the basic norm() function after having loaded using LinearAlgebra; In the lines below, `Phi`

is a matrix created in the middle of a larger program.

```
julia> typeof(Phi)
Array{Float64,2}
julia> x = Phi[:,1];
julia> typeof(x)
Array{Float64,1}
julia> norm(x)
ERROR: MethodError: objects of type Array{Float64,2} are not callable
Use square brackets [] for indexing an Array.
Stacktrace:
[1] top-level scope at REPL[24]:1
```

Can anyone tell me what this error message means ? Thank you.