# Convert an array into Int

**URL:** <https://discourse.julialang.org/t/convert-an-array-into-int/26335>\
**Category:** New to Julia\
**Tags:** arrays, convert\
**Created:** [July 14, 2019, 6:35am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335 "2019-07-14T06:35:48Z")\
**Posts on this page:** 11\
**Page:** 1

<div class="post-metadata">

**Author:** ![MuadhF](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/muadhf/32/20389_2.png) [@MuadhF](https://discourse.julialang.org/u/MuadhF)\
**Post date:** [July 14, 2019, 6:35am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/1 "2019-07-14T06:35:48Z")

</div>

Hi,

If I have an 2D array of multiple elements (named aux), how do I convert or ensure that they are integers? Also note that I didn’t create this array, it was copied from a dataframe, which was in turn taken from a CSV file. I don’t know if that is relevant but thought it might be better to mention. I tried round(Int, aux) but it doesn’t work. I get the following error:

```julia
ERROR: MethodError: objects of type Array{ConstraintRef{Model,C,Shape} where Shape<:AbstractShape where C,1} are not callable
Use square brackets [] for indexing an Array.

```

Here’s an MWE

```julia
df2 = DataFrame(csv2)
aux = df2.T

```

Thanks!

---

<div class="post-metadata">

**Author:** ![johnh](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/johnh/32/3615_2.png) [@johnh](https://discourse.julialang.org/u/johnh)\
**Post date:** [July 14, 2019, 7:11am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/2 "2019-07-14T07:11:47Z")

</div>

Try using the convert function

convert(T, x)

Convert x to a value of type T.

If T is an Integer type, an InexactError will be raised if x is not representable by T, for example if x is not  
integer-valued, or is outside the range supported by T.

Examples  
≡≡≡≡≡≡≡≡≡≡

julia\> convert(Int, 3.0)  
3

julia\> convert(Int, 3.5)  
ERROR: InexactError: Int64(3.5)  
Stacktrace:  
[…]

If T is a AbstractFloat or Rational type, then it will return the closest value to x representable by T.

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<div class="post-metadata">

**Author:** ![MuadhF](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/muadhf/32/20389_2.png) [@MuadhF](https://discourse.julialang.org/u/MuadhF)\
**Post date:** [July 14, 2019, 7:24am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/3 "2019-07-14T07:24:42Z")

</div>

Thanks for the suggestion, but it doesn’t accept arrays apparerntly. So I tried using a for loop

```julia
for i = 1:100 
     convert(Int, aux[i])
end

```

I think it momentarily converts to integer but then it goes back to float. The entire array is actually integer except for one value, because I wanted to experiment. But because of that one float value, the entire array becomes float.

```julia
julia> aux[1]
1.0

julia> convert(Int, aux[1])
1

julia> aux[1]
1.0

```

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<div class="post-metadata">

**Author:** ![johnh](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/johnh/32/3615_2.png) [@johnh](https://discourse.julialang.org/u/johnh)\
**Post date:** [July 14, 2019, 7:38am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/4 "2019-07-14T07:38:03Z")

</div>

This documentation might help  
[https://docs.julialang.org/en/v1/manual/conversion-and-promotion/](https://docs.julialang.org/en/v1/manual/conversion-and-promotion/)

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<div class="post-metadata">

**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [July 14, 2019, 7:46am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/5 "2019-07-14T07:46:49Z")

</div>

The element type of an array is fixed and cannot be changed. You can create a new array with the result of converting all elements to Int with e.g. `Int.(aux)`.

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<div class="post-metadata">

**Author:** ![MuadhF](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/muadhf/32/20389_2.png) [@MuadhF](https://discourse.julialang.org/u/MuadhF)\
**Post date:** [July 14, 2019, 7:58am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/6 "2019-07-14T07:58:22Z")

</div>

Thank you!

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<div class="post-metadata">

**Author:** ![scotts](https://avatars.discourse-cdn.com/v4/letter/s/ac8455/32.png) [@scotts](https://discourse.julialang.org/u/scotts)\
**Post date:** [September 8, 2020, 12:46am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/7 "2020-09-08T00:46:48Z")

</div>

This works great. So, why doesn’t it work when I put it in a loop?

I have a Dict ‘m’ with several arrays of floats I want to convert to ints.

No problem going though the individual Arrays in this dict one by one:

m[“Array1”] = Int.(m[“Array1”])  
m[“Array1”] = Int.(m[“Array1”])  
…

This works perfectly, but when I try to make a loop to process the multiple arrays in less lines, like:

for i in [m[“Array1”], m[“Array2”], m[“Array3”]]  
i = Int.(i)  
end

They don’t convert… ☹

How can I get Int.(…) working in a loop like this???

(not) working example below:

```julia
julia> for i in [m["max_age"],m["type_id"]]
       i = Int.(i)
       end

julia> m["type_id"]
5×2 Array{Float64,2}:
 1.0 2.0
 0.0 1.0
 1.0 2.0
 1.0 3.0
 0.0 3.0

julia> m["type_id"] = Int.(m["type_id"])
5×2 Array{Int64,2}:
 1 2
 0 1
 1 2
 1 3
 0 3

```

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<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [September 8, 2020, 1:25am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/8 "2020-09-08T01:25:16Z")

</div>

> [@scotts](#):
>
> for i in [m[“Array1”], m[“Array2”], m[“Array3”]]  
> i = Int.(i)  
> end

Do

```julia
for i in [m["Array1"], m["Array2"], m["Array3"]]
    i .= Int.(i)
end

```

instead.

Note the dot in the assignment.

Also see my [recent post about bindings/labels](https://discourse.julialang.org/t/is-it-appropriate-to-say-a-variable-is-a-label-or-box/46068/19).

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<div class="post-metadata">

**Author:** ![scotts](https://avatars.discourse-cdn.com/v4/letter/s/ac8455/32.png) [@scotts](https://discourse.julialang.org/u/scotts)\
**Post date:** [September 8, 2020, 1:37am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/9 "2020-09-08T01:37:24Z")

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Didn’t work ☹

```julia
ERROR: LoadError: MethodError: no method matching copyto!(::Float64, ::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{0},Tuple{},Type{Int64},Tuple{Float64}})
Closest candidates are:
  copyto!(::AbstractArray, ::Base.Broadcast.Broadcasted{var"#s826",Axes,F,Args} where Args<:Tuple where F where Axes where var"#s826"<:Base.Broadcast.AbstractArrayStyle{0}) at broadcast.jl:889
  copyto!(::AbstractArray, ::Base.Broadcast.Broadcasted) at broadcast.jl:886
  copyto!(::AbstractArray, ::Any) at abstractarray.jl:730

```

Weird, as it works when I write them out line for line (without the dot in the assignment), as in my above post…

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<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [September 8, 2020, 1:54am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/10 "2020-09-08T01:54:19Z")

</div>

Ah, of course, my bad, the type of the Array is concrete and you cannot change its contents this way, you really need to allocate a new Array. The solution then is:

```julia
for i in ("Array1", "Array2", "Array3")
    m[i] = Int.(m[i])
end

```

You need to change to what `m` is pointing to, so you need to change it some way. This ends up in what I say in my post. There are no boxes there. `i` is just a name, you create a whole new array with `Int.(i)`, and you change `i` to refer to it; but `i` is just a label, it is not a box, changing what `i` refer to will not update anything, it is not a memory position that is shared by `m`.

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<div class="post-metadata">

**Author:** ![scotts](https://avatars.discourse-cdn.com/v4/letter/s/ac8455/32.png) [@scotts](https://discourse.julialang.org/u/scotts)\
**Post date:** [September 8, 2020, 1:58am UTC](https://discourse.julialang.org/t/convert-an-array-into-int/26335/11 "2020-09-08T01:58:14Z")

</div>

Works perfect! Requires even less text too

Thanks, Henrique!