Better changelog for 0.2.0.0

Author: mchav

CHANGELOG.md

@@ -1,26 +1,43 @@
 # Revision history for dataframe
 
-## 0.1.0.0
+## 0.2.0.0
+### Remove `Function` adt with a column expression syntax.
 
-* Initial release
+Previously, we tried to stay as close to Haskell as possible. We used the explicit
+ordering of the column names in the first part of the tuple to determine the function
+arguments and the a regular Haskell function that we evaluated piece-wise on each row.
 
-## 0.1.0.1
+```haskell
+let multiply (a :: Int) (b :: Double) = fromIntegral a * b
+let withTotalPrice = D.deriveFrom (["quantity", "item_price"], D.func multiply) "total_price" df
+```
 
-* Fixed parse failure on nested, escaped quotation.
-* Fixed column info when field name isn't found. 
+Now, we have a column expression syntax that mirrors Pyspark and Polars.
 
-## 0.1.0.2
+```haskell
+let withTotalPrice = D.derive "total_price" (D.lift fromIntegral (D.col @Int "quantity") * (D.col @Double"item_price")) df
+```
 
+### Adds a coverage report to the repository (thanks to @oforero)
+We don't have good test coverage right now. This will help us determine where to invest.
+@oforero provided a script to make an HPC HTML report for coverage.
+
+### Convenience functions for comparisons 
+Instead of lifting all bool operations we provide `eq`, `leq` etc.
+
+## 0.1.0.3
+* Use older version of correlation for ihaskell itegration
+
+## 0.1.0.2
 * Change namespace from `Data.DataFrame` to `DataFrame`
 * Add `toVector` function for converting columns to vectors.
 * Add `impute` function for replacing `Nothing` values in optional columns.
 * Add `filterAllJust` to filter out all rows with missing data.
 * Add `distinct` function that returns a dataframe with distict rows.
 
-## 0.1.0.3
-* Use older version of correlation for ihaskell itegration
+## 0.1.0.1
+* Fixed parse failure on nested, escaped quotation.
+* Fixed column info when field name isn't found.
 
-# 0.2.0.0
-* Remove `Function` adt with a column expression syntax.
-* Adds a coverage report to the repository (thanks to @oforero)
-* Convenience functions for comparisons
+## 0.1.0.0
+* Initial release