# DataFrames: convert column data type

**URL:** https://discourse.julialang.org/t/dataframes-convert-column-data-type/35522
**Category:** Data
**Tags:** type, dataframes, convert
**Created:** [March 4, 2020, 3:03pm UTC](https://discourse.julialang.org/t/dataframes-convert-column-data-type/35522 "2020-03-04T15:03:29Z")
**Posts on this page:** 1
**Showing post:** 50

<div class="post-metadata">

### Author: ![Skoffer](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/skoffer/32/378_2.png) [@Skoffer](https://discourse.julialang.org/u/Skoffer)
#### Post date: [March 8, 2021, 10:37am UTC](https://discourse.julialang.org/t/dataframes-convert-column-data-type/35522/50 "2021-03-08T10:37:43Z")

</div>

Your second line do not change dataframe.

```julia
julia> df = DataFrame(B = [23])
1×1 DataFrame
 Row │ B
     │ Int64
─────┼───────
   1 │ 23

julia> string.(df[!,:B])
1-element Vector{String}:
 "23"

julia> df[!, :B]
1-element Vector{Int64}:
 23

```

If you want to make a change, you should reassign column

```julia
julia> df[!, :B] = string.(df[!,:B])
1-element Vector{String}:
 "23"

julia> df[!, :B]
1-element Vector{String}:
 "23"

```

Of course, `Int.` is not working anymore

```julia
julia> Int.(df[!,:B])
ERROR: MethodError: no method matching Int64(::String)

```

---

_[View the full topic](https://discourse.julialang.org/t/dataframes-convert-column-data-type/35522)._