make readme more clear

Author: Zsailer

README.md

@@ -2,19 +2,21 @@
 **The easy way to write your own flavor of Pandas**
 
 Pandas added an new (simple) API to register accessors with Pandas objects.
-This package adds support for registering methods as well.
+This package does two things:
+1. adds support for registering methods as well.
+2. makes each of these functions backwards compatible with older versions of Pandas.
 
-*What does this mean?*
+***What does this mean?***
 
-It's super easy to custom functionality to Pandas DataFrames and Series.
+It is now simpler to add custom functionality to Pandas DataFrames and Series.
 
 Import this package. Write a simple python function. Register the function using one of the following decorators.
 
-*Why?*
+***Why?***
 
 Pandas is super handy. Its general purpose is to be a "flexible and powerful data analysis/manipulation library".
 
-**Pandas Flavor** allows you to tailor Pandas to specific fields or use cases.
+**Pandas Flavor** allows you add functionality that tailors Pandas to specific fields or use cases.
 
 Maybe you want to add new write methods to the Pandas DataFrame? Maybe you want custom plot functionality? Maybe something else?
 
@@ -37,21 +39,43 @@ class MyFlavor(object):
   def __init__(self, data):
     self._data
 
-  def is_cool(self):
-      """Is my accessor cool?"""
-      return True
+    def row_by_value(self, col, value):
+        """Slice out row from DataFrame by a value."""
+        return self._data[self._data[col] == value].squeeze()
+
+```
+
+Every dataframe now has this accessor as an attribute.
+```python
 
 # DataFrame.
-df = DataFrame()
+df = DataFrame(data={
+  "x": [10, 20, 25],
+  "y": [0, 2, 5]
+})
+
+# Print DataFrame
+print(df)
+
+# x  y
+# 0  10  0
+# 1  20  2
+# 2  25  5
+
+# Access this functionality
+df.my_flavor.row_by_value('x', 10)
 
 # Access this functionality
-df.my_flavor.is_cool()
-# Returns True
-True
+df.row_by_value('x', 10)
+
+# x    10
+# y     0
+# Name: 0, dtype: int64
 ```
 
-To see this in action, check out [pdvega](https://github.com/jakevdp/pdvega)! this
-library adds a new plotting accessor for making Vega plots from pandas data.
+To see this in action, check out [pdvega](https://github.com/jakevdp/pdvega) and
+[PhyloPandas](https://github.com/Zsailer/phylopandas)!
+
 
 ## Register methods
 
@@ -63,19 +87,31 @@ import pandas as pd
 import pandas_flavor as pf
 
 @pf.register_dataframe_method
-def is_cool(df):
-    """Is my dataframe cool?"""
-    return True
+def row_by_value(df, col, value):
+    """Slice out row from DataFrame by a value."""
+    return df[df[col] == value].squeeze()
+
+```
 
+```python
 # DataFrame.
-df = DataFrame()
+df = DataFrame(data={
+  "x": [10, 20, 25],
+  "y": [0, 2, 5]
+})
+
+# Print DataFrame
+print(df)
+
+# x  y
+# 0  10  0
+# 1  20  2
+# 2  25  5
 
 # Access this functionality
-df.is_cool()
-# Returns True
-True
-```
+df.row_by_value('x', 10)
 
-To see in action, check out [PhyloPandas](https://github.com/Zsailer/phylopandas).
-This library adds extra `to_` methods for writing DataFrames to various biological
-sequencing file formats.
+# x    10
+# y     0
+# Name: 0, dtype: int64
+```