@replacena not working with variables as replacement value

New to Julia
1

Hi, was trying to practice some simple data cleaning with Query.jl modifying a bit an example of the documentation.

What I intended to do was to replace all the missing values in a column with the mean of that column.

using Queryverse
using Statistics

df = DataFrame(a=[1,2,missing], b=[“One”,missing,“Three”])
myMean = mean(skipmissing(df.a))
q = df |> @replacena(:b=>“Unknown”, :a=>myMean) |> DataFrame

Wich trigered an error.

julia> q = df |> @replacena(:b=>“Unknown”, :a=>myMean) |> DataFrame
ERROR: UndefVarError: myMean not defined

So I decided to try using another function of Query to see if it was expected to work that way.

julia> df |> @mutate(c = myMean)
3x3 query result
a │ b │ c
────┼─────────┼────
1 │ “One” │ 1.5
2 │ #NA │ 1.5
#NA │ “Three” │ 1.5

And it did.

Finally, decided to try without using a variable and just using the function that returns the value wich I was trying to use to replace missing values with.

q = df |> @replacena(:b=>“Unknown”, :a=>mean(skipmissing(_.a))) |> DataFrame

Still got an error.

julia> q = df |> @replacena(:b=>“Unknown”, :a=>mean(skipmissing(_.a))) |> DataFrame
ERROR: UndefVarError: mean not defined

Any help will be apreciated.

2

I can only guess, despite your fine MWE but Queryverse doesn’t compile in my environment (python36.dll missing).
The docs
https://www.queryverse.org/Query.jl/stable/standalonequerycommands/#The-@replacena-command-1
aren’t explicit but talk only about values. So my guess is that
q = df |> @replacena(:b=>"Unknown", :a=> $myMean ) |> DataFrame
could do.
https://docs.julialang.org/en/v1/manual/metaprogramming/#man-expression-interpolation-1

3

Tried with
julia> q = df |> @replacena(:b=>"Unknown", :a=> $myMean ) |> DataFrame

Got
ERROR: syntax: "$" expression outside quote around C:\Users\RoniD\.julia\packages\Query\85Sw7\src\query_translation.jl:58

Also tried with
julia> q = df |> @replacena(:b=>"Unknown", :a=> "$myMean") |> DataFrame

And got another error
ERROR: UndefVarError: myMean not defined

4

Ok, I had to remove my .julia to get a working Queryverse#master. This is the working syntax:

julia> using DataFrames, Queryverse, Statistics

julia> df = DataFrame(a=[1,2,missing], b=["One",missing,"Three"])
3×2 DataFrame
│ Row │ a       │ b       │
│     │ Int64?  │ String? │
├─────┼─────────┼─────────┤
│ 1   │ 1       │ One     │
│ 2   │ 2       │ missing │
│ 3   │ missing │ Three   │

julia> myMean = mean(skipmissing(df.a))
1.5

julia> q = df |> @replacena(:b=>"Unknown", :a => :( $myMean ) ) |> DataFrame
3×2 DataFrame
│ Row │ a   │ b       │
│     │ Any │ Any     │
├─────┼─────┼─────────┤
│ 1   │ 1   │ One     │
│ 2   │ 2   │ Unknown │
│ 3   │ 1.5 │ Three   │
5

Thanks!
It does work now.