# Status of @tranform altering columns in DataFramesMeta

**URL:** <https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904>\
**Category:** Data\
**Created:** [March 22, 2018, 8:13pm UTC](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904 "2018-03-22T20:13:58Z")\
**Posts on this page:** 6\
**Page:** 1

<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:** [March 22, 2018, 8:13pm UTC](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904/1 "2018-03-22T20:13:58Z")

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What is the status of altering a column that has already been altered in a `@tranform` block with DataFramesMeta?

I have a dataframe with some messy descriptions in years and months in spanish, and I need to do some cleaning before I can use regex to get two numeric columns for years and months.

```julia

df = DataFrame(length_of_contact = ["25 AÑOS", "5 años 9 meses", "15 años "])

df = @transform(df, 
	length_of_contact = lowercase.(:length_of_contact),
	length_of_contact = replace.(:length_of_contact, "Ñ", "n"),
	length_of_contact = replace.(:length_of_contact, "ñ", "n"),
	length_of_contact = replace.(:length_of_contact, "7meses", "7 meses"))

```

The issue is that each time I refer to `:length_of_contact`, DataFramesMeta refers to the column `:length_of_contact` _before_ the beginning of the `@tranform` block. Rather, I would like to perform a set of small sequential changes on the variable.

Am I going about this process the wrong way? Or is there a PR in the `0.7` build that might fix this (I am using `0.6.2`)? Obviously, i could imagine that this isn’t trivial due to the metaprogramming involved.

Thanks

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<div class="post-metadata">

**Author:** ![tbeason](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tbeason/32/15898_2.png) [@tbeason](https://discourse.julialang.org/u/tbeason)\
**Post date:** [March 22, 2018, 8:31pm UTC](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904/2 "2018-03-22T20:31:35Z")

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My guess is that when you write it like that it does not work them sequentially as you might expect.

You could try

```julia
df = @linq df |>
   transform(length_of_contact = lowercase.(:length_of_contact)) |>
   transform(length_of_contact = replace.(:length_of_contact, "Ñ", "n")) |>
   transform(length_of_contact = replace.(:length_of_contact, "ñ", "n")) |>
   transform(length_of_contact = replace.(:length_of_contact, "7meses", "7 meses"))

```

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<div class="post-metadata">

**Author:** ![nalimilan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nalimilan/32/147_2.png) [@nalimilan](https://discourse.julialang.org/u/nalimilan)\
**Post date:** [March 22, 2018, 8:41pm UTC](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904/3 "2018-03-22T20:41:51Z")

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Why not apply all operations at the same time? I.e. `lowercase.(replace.(replace.(...)))`? That should also be more efficient.

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**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:** [March 22, 2018, 8:42pm UTC](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904/4 "2018-03-22T20:42:25Z")

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Yes I am trying to use Lazy.jl to do this right now. Hopefully I will figure it out!

EDIT: I was able to figure it out, for the most part.

This works:

```julia
df = @transform(df, 
	length_of_contact = @> :length_of_contact lowercase.() replace.("ñ", "n")) 

```

But this throws an error:

```julia

df = @transform(df, 
	length_of_contact = @> :length_of_contact 
        lowercase.() 
        replace.("ñ", "n")) 

```

It tells me

```julia
ERROR: LoadError: syntax: missing comma or ) in argument list
Stacktrace:
 [1] include_from_node1(::String) at .\loading.jl:576
 [2] include(::String) at .\sysimg.jl:14
while loading C:\Users\Pdeffebach\Documents\cleaning\julia_cleaning.jl, in expression starting on line 49

```

I think the second way is much more readable. Does anyone know how hard it would be to get Lazy to work with new lines like that?

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<div class="post-metadata">

**Author:** ![bramtayl](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/bramtayl/32/3614_2.png) [@bramtayl](https://discourse.julialang.org/u/bramtayl)\
**Post date:** [March 22, 2018, 8:46pm UTC](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904/5 "2018-03-22T20:46:31Z")

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```julia
@> begin
    :length_of_contact 
    lowercase.() 
    replace.("ñ", "n"))
end

```

---

<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:** [March 22, 2018, 8:49pm UTC](https://discourse.julialang.org/t/status-of-tranform-altering-columns-in-dataframesmeta/9904/6 "2018-03-22T20:49:15Z")

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This is it, thanks!

This syntax is incredibly readable and concise. Thanks to the contributors of Lazy.jl and DataFramesMeta.jl! I am working on something that compares a data cleaning task in Stata and Julia, and I was expecting Stata to be more readable, but maybe not!