Bug: Rounding Error in Tests

[elbow-jason]

Hi all!

It seems that I have encountered a rounding error. While this is certainly a bug, I don't consider it to be very significant; maybe the least significant.

When I run tests with mix test on main I get a failed test:

1) doctest Explorer.DataFrame.summarise/2 (175) (Explorer.DataFrameTest)
     test/explorer/data_frame_test.exs:9
     Doctest failed
     doctest:
       iex> df = Explorer.Datasets.iris()
       iex> Explorer.DataFrame.summarise(df, mean_petal_length: mean(petal_length))
       #Explorer.DataFrame<
         Polars[1 x 1]
         mean_petal_length f64 [3.758666666666666]
       >
     code:  inspect(Explorer.DataFrame.summarise(df, mean_petal_length: mean(petal_length))) === "#Explorer.DataFrame<\n  Polars[1 x 1]\n  mean_petal_length f64 [3.758666666666666]\n>"
     left:  "#Explorer.DataFrame<\n  Polars[1 x 1]\n  mean_petal_length f64 [3.758666666666667]\n>"
     right: "#Explorer.DataFrame<\n  Polars[1 x 1]\n  mean_petal_length f64 [3.758666666666666]\n>"
     stacktrace:
       lib/explorer/data_frame.ex:5399: Explorer.DataFrame (module)

My machine is MacBook M1 on Sonoma 14.1.1 (23B81):

$ uname -a
Darwin Jasons-MacBook-Pro.local 23.1.0 Darwin Kernel Version 23.1.0: Mon Oct  9 21:28:12 PDT 2023; root:xnu-10002.41.9~6/RELEASE_ARM64_T8103 arm64

Versions:

$ rustc --version
rustc 1.78.0-nightly (397937d81 2024-02-22)

$ iex
Erlang/OTP 26 [erts-14.2.1] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit] [dtrace]

Interactive Elixir (1.15.7) - press Ctrl+C to exit (type h() ENTER for help)

asdf current erlang
erlang          26.2.1          /Users/jason/.tool-versions

Let me know if I need to provide more data about my setup.

[josevalim]

This is somewhat expected for floats. Maybe we should round the value a bit to avoid such cases.