The best way to convert Vector into Matrix in Julia?

Question

Suppose I have a variable v of a type Vector.

What would be the best / fastest way to just convert it into Matrix representation (for whatever reason)?

To clarify, v'' will do the job, but is it the best way to do this?

Solution 1

Reshape should be the most efficient. From the docs:

reshape(A, dims): Create an array with the same data as the given array, but with different dimensions. An implementation for a particular type of array may choose whether the data is copied or shared.

julia> v = rand(3)
3-element Array{Float64,1}:
 0.690673 
 0.392635 
 0.0519467

julia> reshape(v, length(v), 1)
3x1 Array{Float64,2}:
 0.690673 
 0.392635 
 0.0519467

Solution 2

v[:,:] is probably the clearest way to do this.

For example:

julia> v=[1,2,3]
3-element Array{Int64,1}:
1
2
3

julia> m=v[:,:]
3x1 Array{Int64,2}:
1
2
3

julia> ndims(m)
2

Solution 3

Or just use:

v = [1, 2, 3]
hcat(v)

Result:

3×1 Array{Int64,2}:
 1
 2
 3

Comments

[amrods]

try using reshape.

[Colin T Bowers]

Just noting that in v0.6, v'' will no longer work, as this now converts v into a row vector, then back into a vector. reshape (as described below) is probably the best solution.

[Jollywatt]

We can now use reshape(v, :, 1), instead of finding length(v) explicitly. docs.julialang.org/en/v1/base/arrays/#Base.reshape

[aberdysh]

This will allocate, so better to use reshape