# How to force mixed-type array of just ints and floats?

**URL:** <https://discourse.julialang.org/t/how-to-force-mixed-type-array-of-just-ints-and-floats/10934>\
**Category:** General Usage\
**Tags:** question\
**Created:** [May 16, 2018, 6:27pm UTC](https://discourse.julialang.org/t/how-to-force-mixed-type-array-of-just-ints-and-floats/10934 "2018-05-16T18:27:50Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![ronubi](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ronubi/32/4085_2.png) [@ronubi](https://discourse.julialang.org/u/ronubi)\
**Post date:** [May 16, 2018, 6:27pm UTC](https://discourse.julialang.org/t/how-to-force-mixed-type-array-of-just-ints-and-floats/10934/1 "2018-05-16T18:27:50Z")

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I’d like to store a table as a mixed-type numeric array - just ints and floats.

If I use [brackets] to initialize a vector of numeric values, Julia promotes the ints to floats and returns an array of floats. If I include a non-numeric type (e.g. string) as the last value and then pop! the vector (or subset it to a the index range of numeric-only values), it preserves the remaining numbers in an Any-type vector. Is there a way to do this without including then removing a non-numeric value?

```
v = [1.5,1,"foo"]; pop!(v); # v is now a length-2 Vector{Any} 
v = [1.5,1]; # v here is a Vector{Float64}

```

Apologies in advance if this has already been answered. I _did_ do a search before posting.

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**Author:** ![mauro3](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mauro3/32/292_2.png) [@mauro3](https://discourse.julialang.org/u/mauro3)\
**Post date:** [May 16, 2018, 6:31pm UTC](https://discourse.julialang.org/t/how-to-force-mixed-type-array-of-just-ints-and-floats/10934/2 "2018-05-16T18:31:04Z")

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You pre-pend the eltype:

```julia
Any[5,6]

```

gives an `Array{Any,1}`. To just store ints and floats you could do  
`Union{Int,Float64}[5, 6, 9.0]` or maybe just `Real[1, 2.0]`.

Edit: note that performance maybe worse with heterogeneous arrays.

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**Author:** ![ronubi](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ronubi/32/4085_2.png) [@ronubi](https://discourse.julialang.org/u/ronubi)\
**Post date:** [May 16, 2018, 6:35pm UTC](https://discourse.julialang.org/t/how-to-force-mixed-type-array-of-just-ints-and-floats/10934/3 "2018-05-16T18:35:19Z")

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Thanks for the quick answer, mauro3!

I wasn’t aware of the `T[]` syntax for arrays.

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**Author:** ![stillyslalom](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stillyslalom/32/45687_2.png) [@stillyslalom](https://discourse.julialang.org/u/stillyslalom)\
**Post date:** [May 16, 2018, 6:44pm UTC](https://discourse.julialang.org/t/how-to-force-mixed-type-array-of-just-ints-and-floats/10934/4 "2018-05-16T18:44:59Z")

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Something to note: there’s a big jump in performance for functions acting on small union types between Julia 0.6 and 0.7, although operations on arrays of `Real`s don’t seem to have changed:

```julia
# v0.6.2
using BenchmarkTools
u = Union{Int64, Float64}[rand() < 0.5 ? 1 : 1.0 for i = 1:1000]
v = Real[rand() < 0.5 ? 1 : 1.0 for i = 1:1000]

@btime sum($u) # -> 42.516 μs (3466 allocations: 54.16 KiB)
@btime sum($v) # -> 27.661 μs (1000 allocations: 15.63 KiB)

```

vs.

```julia
# v0.7.0-DEV.5075
using BenchmarkTools
u = Union{Int64, Float64}[rand() < 0.5 ? 1 : 1.0 for i = 1:1000]
v = Real[rand() < 0.5 ? 1 : 1.0 for i = 1:1000]

@btime sum($u) # -> 9.788 μs (0 allocations: 0 bytes)
@btime sum($v) # -> 25.940 μs (999 allocations: 15.61 KiB)

```

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<div class="post-metadata">

**Author:** ![mauro3](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mauro3/32/292_2.png) [@mauro3](https://discourse.julialang.org/u/mauro3)\
**Post date:** [May 16, 2018, 8:26pm UTC](https://discourse.julialang.org/t/how-to-force-mixed-type-array-of-just-ints-and-floats/10934/5 "2018-05-16T20:26:09Z")

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> [@stillyslalom](#):
>
> `Real` s don’t seem to have changed:

Yep, `Real`s are not a small union, anything but as this post nicely describes: [Type stability for returning abstract types - #2 by mbauman](https://discourse.julialang.org/t/type-stability-for-returning-abstract-types/10890/2)