Change index.md for data-science-tools/Pandas (#30342)

Added applying functions & selecting data in Pandas

guide/english/data-science-tools/pandas/index.md

@@ -147,6 +147,40 @@ right = pd.DataFrame({'C': ['C0', 'C2', 'C3'],
 ```python
 left.join(right)
 ```
+# Pandas Functions
+## Information on Unique Values
+```python
+df['col1'].unique()
+```
+```python
+df['col1'].nunique()
+```
+```python
+df['col1'].value_counts()
+```
+## Selecting Data
+```python
+newdf = df[(df['col1']>2) & (df['col2']==123)]
+```
+```python
+newdf
+```
+## Applying Functions
+```python
+def times2(x):
+    return x*2
+```
+```python
+df['col1'].apply(times2)
+```
+
+```python
+df['col1'].apply(len)
+```
+## Permanently removing a column
+```python
+del df['col1']
+```
 
 #### More Information:
 1. [pandas](http://pandas.pydata.org/)