Search code examples
dataframejuliadataframes.jl

Apply "any" or "all" function row-wise to arbitrary number of Boolean columns in Julia DataFrames.jl


Suppose I have a dataframe with multiple boolean columns representing certain conditions:

df = DataFrame(
         id = ["A", "B", "C", "D"], 
         cond1 = [true, false, false, false], 
         cond2 = [false, false, false, false], 
         cond3 = [true, false, true, false]
)
id cond1 cond2 cond3
1 A 1 0 1
2 B 0 0 0
3 C 0 0 1
4 D 0 0 0

Now suppose I want to identify rows where any of these conditions are true, ie "A" and "C". It is easy to do this explicitly:

df[:, :all] = df.cond1 .| df.cond2 .| df.cond3

But how can this be done when there are an arbitrary number of conditions, for example something like:

df[:, :all] = any.([ df[:, Symbol("cond$i")] for i in 1:3 ])

The above fails with DimensionMismatch("tried to assign 3 elements to 4 destinations") because the any function is being applied column-wise, rather than row-wise. So the real question is: how to apply any row-wise to multiple Boolean columns in a dataframe?

The ideal output should be:

id cond1 cond2 cond3 all
1 A 1 0 1 1
2 B 0 0 0 0
3 C 0 0 1 1
4 D 0 0 0 0

Solution

  • Here is one way to do it:

    julia> df = DataFrame(
                    id = ["A", "B", "C", "D", "E"],
                    cond1 = [true, false, false, false, true],
                    cond2 = [false, false, false, false, true],
                    cond3 = [true, false, true, false, true]
           )
    5×4 DataFrame
     Row │ id      cond1  cond2  cond3
         │ String  Bool   Bool   Bool
    ─────┼─────────────────────────────
       1 │ A        true  false   true
       2 │ B       false  false  false
       3 │ C       false  false   true
       4 │ D       false  false  false
       5 │ E        true   true   true
    
    julia> transform(df, AsTable(r"cond") .=> ByRow.([maximum, minimum]) .=> [:any, :all])
    5×6 DataFrame
     Row │ id      cond1  cond2  cond3  any    all
         │ String  Bool   Bool   Bool   Bool   Bool
    ─────┼───────────────────────────────────────────
       1 │ A        true  false   true   true  false
       2 │ B       false  false  false  false  false
       3 │ C       false  false   true   true  false
       4 │ D       false  false  false  false  false
       5 │ E        true   true   true   true   true
    

    Note that it is quite fast even for very wide tables:

    julia> df = DataFrame(rand(Bool, 10_000, 10_000), :auto);
    
    julia> @time transform(df, AsTable(r"x") .=> ByRow.([maximum, minimum]) .=> [:any, :all]);
      0.059275 seconds (135.41 k allocations: 103.038 MiB)
    

    In the examples I have used a regex column selector, but of course you can use any row selector you like.