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software:python [2019/10/05 00:35] – [Pandas] christiansoftware:python [2021/12/14 20:36] (current) – [Pandas/Geopandas] christian
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-==== Pandas ====+==== Pandas/Geopandas ====
  
-  * Invert a single column of a Pandas Dataframe: ``df.col2 = df.col2.values[::-1]`` [[https://stackoverflow.com/questions/46244235/invert-a-single-column-in-a-dataframe|via StackOverflow]] +  * Invert a single column of a Pandas Dataframe: ''df.col2 = df.col2.values[::-1]'' [[https://stackoverflow.com/questions/46244235/invert-a-single-column-in-a-dataframe|via StackOverflow]] 
-  * Joining multiple overlapping column names from multiple dataframes: ``pd.concat(data, axis=1)`` [[https://stackoverflow.com/questions/13003769/joining-multiple-dataframes-with-pandas-with-overlapping-column-names|via StackOverflow]] +  * Joining multiple overlapping column names from multiple dataframes: ''pd.concat(data, axis=1)'' [[https://stackoverflow.com/questions/13003769/joining-multiple-dataframes-with-pandas-with-overlapping-column-names|via StackOverflow]] 
-  * Cross-section indexing of a multi-indexed dataframe - using levels: ``concatdf.xs('MIndexValue', level='MIndexName')`` - [[http://pandas-docs.github.io/pandas-docs-travis/user_guide/advanced.html#advanced-xs|via Pandas documentation]] and [[https://stackoverflow.com/questions/24435788/using-loc-with-a-multiindex-in-pandas#24436783|StackOverflow]]+  * Cross-section indexing of a multi-indexed dataframe - using levels: ''concatdf.xs('MIndexValue', level='MIndexName')'' - [[http://pandas-docs.github.io/pandas-docs-travis/user_guide/advanced.html#advanced-xs|via Pandas documentation]] and [[https://stackoverflow.com/questions/24435788/using-loc-with-a-multiindex-in-pandas#24436783|StackOverflow]]
   * [[https://stackoverflow.com/questions/53645882/pandas-merging-101|Pandas merging 101]] on StackOverflow.   * [[https://stackoverflow.com/questions/53645882/pandas-merging-101|Pandas merging 101]] on StackOverflow.
- +  * Going from a regular dataframe to geopandas data frame: ''gdf = geopandas.GeoDataFrame(df, geometry=geopandas.points_from_xy(df.Longitude, df.Latitude))'' -- [[https://geopandas.readthedocs.io/en/latest/gallery/create_geopandas_from_pandas.html|via Geopandas doc]] 
 +  * Obtaining unique values for Multi-index levels: ''concatdf.index.unique(level=1)'' 
 +  * Drop a level of multi-index into a column: ''df.reset_index(level=[...])'' - via [[https://stackoverflow.com/questions/20110170/turn-pandas-multi-index-into-column|StackOverflow]] 
 +  * Generating a column with conditional values based on an existing column [[https://datagy.io/pandas-conditional-column/|via datagy.io]]: ''myDict = { 'a': 1, 'b': 2, 'c': 3}'', ''df[newCol] = df[oldCol].map( myDict )''