readme and licence

LICENSE

@@ -0,0 +1,19 @@
+Copyright (c) 2020 Ritchie Vink
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -0,0 +1,69 @@
+# Polars
+---
+
+## In memory DataFrames in Rust
+
+This is my mock up of DataFrames implemented in Rust, using Apache Arrow as backend.
+
+## WIP
+
+### Series
+- [x] cast
+- [x] take by index/ boolean mask
+- [x] Rust iterators
+- [x] append
+- [x] aggregation: min, max, sum
+- [x] arithmetic
+- [x] comparison
+- [ ] find
+- [ ] sorting (can be done w/ iterators)
+
+### DataFrame
+- [x] selection
+- [x] join: inner, left
+- [ ] group by
+- [x] concat (horizontal)
+- [x] read csv
+- [ ] write csv
+- [ ] write json
+- [ ] read json
+- [ ] sorting
+
+### Data types
+- [x] null
+- [x] boolean
+- [x] u32
+- [x] i32
+- [x] i64
+- [x] f32
+- [x] f64
+- [x] utf-8
+- [ ] date
+- [ ] timestamp
+
+
+## Example
+
+```rust
+let s0 = Series::init("days", [0, 1, 2, 3, 4].as_ref());
+let s1 = Series::init("temp", [22.1, 19.9, 7., 2., 3.].as_ref());
+let temp = DataFrame::new_from_columns(vec![s0, s1]).unwrap();
+
+let s0 = Series::init("days", [1, 2].as_ref());
+let s1 = Series::init("rain", [0.1, 0.2].as_ref());
+let rain = DataFrame::new_from_columns(vec![s0, s1]).unwrap();
+let joined = temp.left_join(&rain, "days", "days");
+println!("{}", joined.unwrap())
+```
+
+```text
+           days           temp           rain
+            i32            f64            f64
+            ---            ---            ---
+
+              0           22.1           null
+              1           19.9            0.1
+              2              7            0.2
+              3              2           null
+              4              3           nul
+```