= Julia Vectors =

'''Vectors''' are a columnar series of values.

<<TableOfContents>>

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== Description ==

Vectors are instantiated like:

{{{
julia> a = [1,2,3]
3-element Vector{Int64}:
 1
 2
 3
}}}

Vectors cannot ordinarily be created from a range, but using the vertical concatenation operator (`;`) can be a trick to make it work anyway. Consider:

{{{
julia> a = [1:3]
1-element Vector{UnitRange{Int64}}:
 1:3

julia> a = [1:3; ]
3-element Vector{Int64}:
 1
 2
 3
}}}



=== Typing ===

Vectors are required to be a collection of values that are of the same [[Julia/DataTypes|type]]. If those values are not of the same type but have a common promotion type, they are type cast.

{{{
julia> a = [1, 2.3, 4//5]
3-element Vector{Float64}:
 1.0
 2.3
 0.8
}}}

The values can also be explicitly type cast when instantiated.

{{{
julia> Float32[1, 2.3, 4//5]
3-element Vector{Float32}:
 1.0
 2.3
 0.8
}}}

The `Vector` type itself [[Julia/DataTypes#Abstract_Types|descends]] from `AbstractArray`, just like the [[Julia/Matrices|Matrix]] type.



=== Comparison to Row Vectors ===

While columnar series are of type `Vector`, row series are of type `Matrix` and inherently are 2-dimensional. Most vector operations will not work on a row 'vector'. This is a simple mistake to make; consider:

{{{
julia> a = [1,2,3]
3-element Vector{Int64}:
 1
 2
 3

julia> b = [1 2 3]
1×3 Matrix{Int64}:
 1  2  3
}}}

To flatten a 2-dimensional matrix into a vector, try the `vec()` function.

Note that when given an actual `Matrix` argument, the columns are extracted and stacked.

{{{
julia> b = [1 2 3; 4 5 6]
2×3 Matrix{Int64}:
 1  2  3
 4  5  6

julia> c = vec(b)
6-element Vector{Int64}:
 1
 4
 2
 5
 3
 6
}}}



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