Jolan Rensen

Don't think it's necessary to have a separate file. It's pretty trivial to get a sample: ```json [ { "a": 1 }, { "a": "hi" } ] ``` similar for...

What's wrong about the output?

I suspect this is because recentDelays is a column group with only `Int?` columns, so you try to sum no columns. Sum can only accept Numbers, so it assumes you...

https://github.com/Kotlin/dataframe/pull/937 will remove the exception, but not solve the issue. The `emptyDataFrame().sum { none().cast() }` will now be `0.0` (and a classCastException). There's still the odd switch to `Number` for...

There's actually a lot of places where DataFrame assumes a type based on the file extension, but we should avoid that, as file extensions can be changed while the contents...

Will be solved in the new CSV implementation: "dataframe-csv". I will probably also migrate its new `Compression` class to the :core module in the future to solve reading zips from...

depends on https://github.com/Kotlin/dataframe/pull/372

@zaleslaw not sure, I just ran your `read from huge table` test in `h2Test.kt`, so looking at that file, the connection URL is created like this: https://github.com/Kotlin/dataframe/blob/e781bf7de70a20513b190b959967195fa4795d7f/dataframe-jdbc/src/test/kotlin/org/jetbrains/kotlinx/dataframe/io/h2Test.kt#L21

I've been doing some small performance/size tests [here](https://github.com/Kotlin/dataframe/blob/bfaaec825fd3eb46d47b2b287328db33d0b9ddc0/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/columns/ColumnDataHolder.kt) and I've come to the following results: ### 50k rows ``` ⌌-------------------------------------------------------------------⌍ | | type| creation| processing| size| |--|----------------------|-----------|------------|----------------| | 0| BOXED_ARRAY_WITH_NULL|...

I've updated `ColumnDataHolder` in such a way that it can store a collection/array of nullable primitives: - nulls are filled with `0` (or the zero-equivalent of that type) - indices...