# How to extract substring of a Julia Dataframe column

**URL:** <https://discourse.julialang.org/t/how-to-extract-substring-of-a-julia-dataframe-column/41610>\
**Category:** General Usage\
**Created:** [June 17, 2020, 5:15pm UTC](https://discourse.julialang.org/t/how-to-extract-substring-of-a-julia-dataframe-column/41610 "2020-06-17T17:15:46Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Julia1](https://avatars.discourse-cdn.com/v4/letter/j/db5fbb/32.png) [@Julia1](https://discourse.julialang.org/u/Julia1)\
**Post date:** [June 17, 2020, 5:15pm UTC](https://discourse.julialang.org/t/how-to-extract-substring-of-a-julia-dataframe-column/41610/1 "2020-06-17T17:15:46Z")

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Hi, I may be overthinking this one, but all I’m trying to do is turn a column into a specific indexed substring of that column.

```julia
df = DataFrame(number=[123456,134553])
df[:number] = string.(df[:number]

```

All I want to do is return the first 3 digits of each row value for the numbers column, in this case “123” and “134”.

Thanks

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<div class="post-metadata">

**Author:** ![nilshg](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nilshg/32/2283_2.png) [@nilshg](https://discourse.julialang.org/u/nilshg)\
**Post date:** [June 17, 2020, 5:20pm UTC](https://discourse.julialang.org/t/how-to-extract-substring-of-a-julia-dataframe-column/41610/2 "2020-06-17T17:20:47Z")

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```julia
julia> getindex.(string.(a), Ref(1:3))
2-element Array{String,1}:
 "123"
 "134"

```

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<div class="post-metadata">

**Author:** ![pdeffebach](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pdeffebach/32/10320_2.png) [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)\
**Post date:** [June 17, 2020, 5:20pm UTC](https://discourse.julialang.org/t/how-to-extract-substring-of-a-julia-dataframe-column/41610/3 "2020-06-17T17:20:50Z")

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Note, you should be using the non-deprecated indexing behavior for data frames, i.e. `df[:, :number]` or `df.number`

```julia
julia> df.str_sub_number = SubString.(string.(df.number), 1, 3)

```

If you don’t want to worry about `SubString`s, do

```julia
julia> df.str_sub_number = getindex.(string.(df.number), Ref(1:3))

```

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<div class="post-metadata">

**Author:** ![Julia1](https://avatars.discourse-cdn.com/v4/letter/j/db5fbb/32.png) [@Julia1](https://discourse.julialang.org/u/Julia1)\
**Post date:** [June 17, 2020, 5:38pm UTC](https://discourse.julialang.org/t/how-to-extract-substring-of-a-julia-dataframe-column/41610/4 "2020-06-17T17:38:31Z")

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cool thank you!