# \[ANN\] MissingsAsFalse.jl: Treat missing as false in select operations

**URL:** <https://discourse.julialang.org/t/ann-missingsasfalse-jl-treat-missing-as-false-in-select-operations/70062>\
**Category:** Data\
**Tags:** missing-values\
**Created:** [October 19, 2021, 8:38pm UTC](https://discourse.julialang.org/t/ann-missingsasfalse-jl-treat-missing-as-false-in-select-operations/70062 "2021-10-19T20:38:28Z")\
**Posts on this page:** 2\
**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:** [October 19, 2021, 8:38pm UTC](https://discourse.julialang.org/t/ann-missingsasfalse-jl-treat-missing-as-false-in-select-operations/70062/1 "2021-10-19T20:38:29Z")

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Hello everyone! I am pleased to announce the release of a new package: [MissingsAsFalse.jl](https://github.com/pdeffebach/MissingsAsFalse.jl). As the name implies, it helps you write code where comparisons with `missing` are treated as false. Which is often what is needed in data-cleaning operations.

MissingsAsFalse.jl provides a single macro, `@mfalse`, which sets treats `missing` values as false in select operations. These include

- Comparisons, `==`, `>`, `<`, `>=`, and `<=`, as well as their broadcasted equivalents for arrays.
- Control flow, meaning `if` and `elseif`, as well as ternary commands, `a ? b : c`
- Short circuiting compairons, `&&` and `||`
- Boolean indexing, `y[x]` where `x` is a boolean array which contains `missing`.

In Julia, missing values are represents by `missing`. This is equivalent to `NA` in R and `.` in Stata. In Julia, Boolean operations with `missing` also propagate `missing`-ness.

```julia
julia> missing == 1
missing

```

This is philosophically satisfying. Because `missing` values represent what we “don’t know”, it makes sense that we “don’t know” the outcome of a comparison between `missing` and a known object. But this propagation becomes increasingly burdensome when writing complicated code. In particular, control flow in Julia, like `if` statements, error on `missing` values.

```julia
julia> if missing == 1
           println("Hello, Earth")
       else
           println("Hello, Mars")
       end
ERROR: TypeError: non-boolean (Missing) used in boolean context
Stacktrace:
 [1] top-level scope
   @ REPL[3]:1

```

In almost all cases, we want the above statement to print `"Hello, Mars"`, instead of throwing an error.

Proper handling of `missing` values requires people to use `isequal(missing, 1)` instead of `missing == 1`. The former will return `false` while the latter will return `missing`, as shown above. But writing `isequal` everywhere is burdensome. To help, MissingsAsFalse.jl provides the macro `@mfalse`. Inside code affected by `@mfalse`, the Boolean comparisons which normally return `missing` instead return `false`.

This works on control flow

```julia
julia> @mfalse if missing == 1
           println("Hello, world")
       else
           println("Hello, Mars")
       end
Hello, Mars

```

Greater than and less than comparisons

```julia
julia> x = missing;

julia> @mfalse if x > 100
           1
       else
           100
       end
100

```

As well as vectorized comparisons `.== `, `.>`, `.<` etc. Note: These will allocate a new array. I would appreciate help on how to accomplish this without too many extra allocations.

Short-circuiting

```julia
julia> @mfalse x == 1 && true
false

julia> @mfalse x == 1 || true
true

```

and boolean indexing

```julia
julia> y = [1, 2, 3, 4];

julia> inds = [true, false, true, missing];

julia> @mfalse y[inds]
2-element Vector{Int64}:
 1
 3

```

For complete documentation, see `julia> ? @mfalse`.

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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:** [October 20, 2021, 3:27pm UTC](https://discourse.julialang.org/t/ann-missingsasfalse-jl-treat-missing-as-false-in-select-operations/70062/2 "2021-10-20T15:27:26Z")

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Thanks. This will probably be easier than using ternary operators everywhere, which is what I had been doing before.