I am expecting [-1 -4] in the Julia example.
On Saturday, December 19, 2015 at 4:42:07 PM UTC-8, Lex wrote:
>
> Hi
>
> In Python, I am able to select values like this:
>
> >>> a = np.matrix([[-1,2],[3,-4]])
> >>> y = np.matrix([1,0])
> >>> a[range(2),y]
> matrix([[2, 3]])
> >>>
>
> Is there any equivalent in Julia or using a loop is the only way?
>
> julia> a
> 2x2 Array{Int64,2}:
> -1 2
> 3 -4
>
> julia> y
> 1x2 Array{Int64,2}:
> 1 2
>
> julia> a[:, y]
> ERROR: MethodError: `index_shape_dim` has no method matching
> index_shape_dim(::Array{Int64,2}, ::Int64, ::Array{Int64,2})
>
> You might have used a 2d row vector where a 1d column vector was required.
> Note the difference between 1d column vector [1,2,3] and 2d row vector [1
> 2 3].
> You can convert to a column vector with the vec() function.
> Closest candidates are:
> index_shape_dim(::Any, ::Any, ::Real...)
> index_shape_dim(::Any, ::Any, ::Colon)
> index_shape_dim(::Any, ::Any, ::Colon, ::Any, ::Any...)
> ...
> in getindex at abstractarray.jl:488
>
> julia> a[:, y[]]
> 2-element Array{Int64,1}:
> -1
> 3
>
> julia> a[:, y[:]]
> 2x2 Array{Int64,2}:
> -1 2
> 3 -4
>
> julia>
>
>
>
