README.md in red_amber-0.1.1 vs README.md in red_amber-0.1.2

@@ -6,12 +6,12 @@
 - Simple API similar to [Rover-df](https://github.com/ankane/rover)
 
 ## Requirements
 
 ```ruby
-gem 'red-arrow',   '~> 7.0.0'
-gem 'red-parquet', '~> 7.0.0' # if you use IO from/to parquet
+gem 'red-arrow',   '>= 7.0.0'
+gem 'red-parquet', '>= 7.0.0' # if you use IO from/to parquet
 gem 'rover-df',    '~> 0.3.0' # if you use IO from/to Rover::DataFrame
 ```
 
 ## Installation
 
@@ -87,15 +87,18 @@
  
 - [x] `column_names`, `keys`
   
   Returns num of column names by an Array.
 
-- [x] `types(class_name: false)`
+- [x] `types`
   
-  Returns types of columns by an Array.
-  If `class_name: true` returns an Array of `Arrow::DataType`.
+  Returns types of columns by an Array of Symbols.
 
+- [x] `data_types`
+
+  Returns types of columns by an Array of `Arrow::DataType`.
+
 - [x] `vectors`
 
   Returns an Array of Vectors.
 
 - [x] `to_h`
@@ -126,25 +129,55 @@
 
 - [x] `inspect(tally_level: 5, max_element: 5)`
 
   Shows some information about self.
 
+```ruby
+hash = {a: [1, 2, 3], b: %w[A B C], c: [1.0, 2, 3]}
+RedAmber::DataFrame.new(hash)
+# =>
+RedAmber::DataFrame : 3 observations(rows) of 3 variables(columns)
+Variables : 2 numeric, 1 string
+# key type   level data_preview
+1 :a  uint8      3 [1, 2, 3]
+2 :b  string     3 [A, B, C]
+3 :c  double     3 [1.0, 2.0, 3.0]
+```
+
   - tally_level: max level to use tally mode
   - max_element: max num of element to show values in each row
 
 ### Selecting
 
-- [x] Selecting columns by `[]`
+- [x] Select columns by `[]` as `[key]`, `[keys]`, `[keys[index]]`
+  - Key in a Symbol: `df[:symbol]`
+  - Key in a String: `df["string"]`
+  - Keys in an Array: `df[:symbol1`, `"string"`, `:symbol2`
+  - Keys in indeces: `df[df.keys[0]`, `df[df.keys[1,2]]`, `df[df.keys[1..]]`
+  - Keys in a Range:
+    A end-less Range can be used to represent keys.
+```ruby
+hash = {a: [1, 2, 3], b: %w[A B C], c: [1.0, 2, 3]}
+df = RedAmber::DataFrame.new(hash)
+df[:b..:c, "a"]
+# =>
+RedAmber::DataFrame : 3 observations(rows) of 3 variables(columns)
+Variables : 2 numeric, 1 string
+# key type   level data_preview
+1 :b  string     3 [A, B, C]
+2 :c  double     3 [1.0, 2.0, 3.0]
+3 :a  uint8      3 [1, 2, 3]
+```
 
-  `[key]`, `[keys]`, `[keys[index]]`
+- [x] Select rows by `[]` as `[index]`, `[range]`, `[array]`
+  - Select a row by index: `df[0]`
+  - Select rows by indeces in a Range: `df[1..2]`
+  - Select rows by indeces in an Array: `df[1, 2]`
+  - Mixed case: `df[2, 0..]`
 
-- [x] Selecting rows by `[]`
+- [x] Select rows from top or bottom
 
-  `[index]`, `[range]`, `[array]`
-
-- [x] Selecting rows from top or bottom
-
   `head(n=5)`, `tail(n=5)`, `first(n=1)`, `last(n=1)`
 
 - [ ] slice
 
 ### Updating
@@ -211,10 +244,12 @@
 
 - [x] `size`, `length`, `n_rows`, `nrow`
 
 - [x] `type`
 
+- [x] `data_type`
+
 - [ ] `each`
 
 - [ ] `chunked?`
 
 - [ ] `n_chunks`
@@ -322,10 +357,10 @@
 ### DSL in a block for faster calculation ?
 
 
 ## Development
 
-```
+```shell
 git clone https://github.com/heronshoes/red_amber.git
 cd red_amber
 bundle install
 bundle exec rake test
 ```