# Sort and dims=1 for vector input
**URL:** https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212
**Category:** New to Julia
**Tags:** question
**Created:** [March 30, 2021, 9:42am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212 "2021-03-30T09:42:03Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@ovt](https://discourse.julialang.org/u/ovt)
#### Post date: [March 30, 2021, 9:42am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/1 "2021-03-30T09:42:03Z")
Hi,
I don’t understand why a function like `sort` doesn’t accept dims=1 for a vector input. Let’s take `b=rand(3)` for instance. `sort(b)` works, but `sort(b,dims=1)` gives an error. It means that, in a case where `size(b,2)` is not fixed, I have to catch when `size(b,2)==1` in order to compute `sort(b)` instead of `sort(b,dims=1)`. Why doesn’t sort behave like that already?
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### Author:  [@ericphanson](https://discourse.julialang.org/u/ericphanson)
#### Post date: [March 30, 2021, 9:54am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/2 "2021-03-30T09:54:05Z")
Julia treats vectors as different than `n x 1` matrices. For example,
```julia
julia> x = rand(4, 1) # 4 x 1 matrix
4×1 Matrix{Float64}:
0.5699429434936178
0.38264907855330454
0.2974011813965416
0.9032771294647794
julia> sort(x; dims=1) # works fine
4×1 Matrix{Float64}:
0.2974011813965416
0.38264907855330454
0.5699429434936178
0.9032771294647794
```
So it’s not about if `size(x,2)==1`, it’s about the type of the object. Usually code where `x` is sometimes a vector and sometimes a matrix is avoided (it’s usually [type unstable](https://docs.julialang.org/en/v1/manual/performance-tips/#Write-%22type-stable%22-functions)), but if `y` is a vector, you can `reshape` it to be an `n x 1` matrix via
```julia
julia> y = rand(4)
4-element Vector{Float64}:
0.2646642144471312
0.5108444025487056
0.17038220190741749
0.6299368977104578
julia> reshape(y, :, 1)
4×1 Matrix{Float64}:
0.2646642144471312
0.5108444025487056
0.17038220190741749
0.6299368977104578
```
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### Author:  [@heliosdrm](https://discourse.julialang.org/u/heliosdrm)
#### Post date: [March 30, 2021, 10:10am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/3 "2021-03-30T10:10:40Z")
Or more compact: `hcat(y)`, although that makes a copy of `y`. (`reshape` keeps the same underlying data).
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### Author:  [@ovt](https://discourse.julialang.org/u/ovt)
#### Post date: [March 30, 2021, 10:13am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/4 "2021-03-30T10:13:53Z")
Thanks for your answer!
Then, how do I extract a column of a matrix and avoid the automatic vector conversion? Is reshape the only built in solution?
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### Author:  [@heliosdrm](https://discourse.julialang.org/u/heliosdrm)
#### Post date: [March 30, 2021, 10:15am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/5 "2021-03-30T10:15:35Z")
> [@ovt](#):
>
> how do I extract a column of a matrix and avoid the automatic vector conversion?
Indexing with ranges that only contain the value of the column you want:
```julia
julia> x = rand(4,2)
4×2 Array{Float64,2}:
0.713682 0.122839
0.488861 0.225701
0.742566 0.451154
0.361401 0.851278
julia> x[:,1:1]
4×1 Array{Float64,2}:
0.7136823322753825
0.48886127651427835
0.7425656894856532
0.3614009764175452
```
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### Author:  [@ovt](https://discourse.julialang.org/u/ovt)
#### Post date: [March 30, 2021, 10:20am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/6 "2021-03-30T10:20:14Z")
Thanks!
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### Author:  [@heliosdrm](https://discourse.julialang.org/u/heliosdrm)
#### Post date: [March 30, 2021, 10:25am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/7 "2021-03-30T10:25:06Z")
And a similar option: indexing with a vector with one element:
```julia
julia> x = rand(4,2)
4×2 Array{Float64,2}:
0.713682 0.122839
0.488861 0.225701
0.742566 0.451154
0.361401 0.851278
julia> x[:,[1]]
4×1 Array{Float64,2}:
0.7136823322753825
0.48886127651427835
0.7425656894856532
0.3614009764175452
```
(The key is that if the type of the index can contain more than one value, it will return a matrix instead of a vector.)
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### Author:  [@DNF](https://discourse.julialang.org/u/DNF)
#### Post date: [March 30, 2021, 10:31am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/8 "2021-03-30T10:31:29Z")
Can’t you just work with vectors instead of one-column matrices?
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### Author:  [@ovt](https://discourse.julialang.org/u/ovt)
#### Post date: [March 30, 2021, 10:38am UTC](https://discourse.julialang.org/t/sort-and-dims-1-for-vector-input/58212/9 "2021-03-30T10:38:08Z")
No because I work with matrices, and column matrices consist of a particular case that I have to take into account.