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Pandas - Create a symmetric matrix that counts the number of records



The Next CEO of Stack OverflowCount the number occurrences of a character in a stringPandas: create two new columns in a dataframe with values calculated from a pre-existing columnHow can I replace all the NaN values with Zero's in a column of a pandas dataframeCreating an empty Pandas DataFrame, then filling it?“Large data” work flows using pandasChange data type of columns in PandasHow do I get the row count of a Pandas dataframe?How to make good reproducible pandas examplesPandas Replace NaN with blank/empty stringPopulating a “count matrix” with combinations of pandas DataFrame rows










2















I have a dataframe that looks like the one below



ID | Value
1 | A
1 | B
1 | C
2 | B
2 | C


I want to create a symmetric matrix of based on Value:



 A B C
A 1 1 1
B 1 2 2
C 1 2 2


This basically indicates how many people have both values (v1,v2). I am currently using for loops to scan the dataframe for every combination but was wondering if there was an easier way to do it using pandas.










share|improve this question


























    2















    I have a dataframe that looks like the one below



    ID | Value
    1 | A
    1 | B
    1 | C
    2 | B
    2 | C


    I want to create a symmetric matrix of based on Value:



     A B C
    A 1 1 1
    B 1 2 2
    C 1 2 2


    This basically indicates how many people have both values (v1,v2). I am currently using for loops to scan the dataframe for every combination but was wondering if there was an easier way to do it using pandas.










    share|improve this question
























      2












      2








      2


      1






      I have a dataframe that looks like the one below



      ID | Value
      1 | A
      1 | B
      1 | C
      2 | B
      2 | C


      I want to create a symmetric matrix of based on Value:



       A B C
      A 1 1 1
      B 1 2 2
      C 1 2 2


      This basically indicates how many people have both values (v1,v2). I am currently using for loops to scan the dataframe for every combination but was wondering if there was an easier way to do it using pandas.










      share|improve this question














      I have a dataframe that looks like the one below



      ID | Value
      1 | A
      1 | B
      1 | C
      2 | B
      2 | C


      I want to create a symmetric matrix of based on Value:



       A B C
      A 1 1 1
      B 1 2 2
      C 1 2 2


      This basically indicates how many people have both values (v1,v2). I am currently using for loops to scan the dataframe for every combination but was wondering if there was an easier way to do it using pandas.







      python pandas






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Mar 8 at 14:26









      NiviNivi

      4101513




      4101513






















          1 Answer
          1






          active

          oldest

          votes


















          3














          Use merge with cross join by ID column with crosstab and DataFrame.rename_axis for remove index and columns names:



          df = pd.merge(df, df, on='ID')

          df = pd.crosstab(df['Value_x'], df['Value_y']).rename_axis(None).rename_axis(None, axis=1)
          print (df)
          A B C
          A 1 1 1
          B 1 2 2
          C 1 2 2





          share|improve this answer




















          • 1





            'Value_x' and 'Value_y' are to be specified or are they inbuilt keywords? Thanks for the help.

            – Nivi
            Mar 8 at 14:30






          • 1





            Got it. Thanks!

            – Nivi
            Mar 8 at 14:46






          • 1





            @Nivi - It is index and columns names created from columns names after crosstab

            – jezrael
            Mar 8 at 14:46











          Your Answer






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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          3














          Use merge with cross join by ID column with crosstab and DataFrame.rename_axis for remove index and columns names:



          df = pd.merge(df, df, on='ID')

          df = pd.crosstab(df['Value_x'], df['Value_y']).rename_axis(None).rename_axis(None, axis=1)
          print (df)
          A B C
          A 1 1 1
          B 1 2 2
          C 1 2 2





          share|improve this answer




















          • 1





            'Value_x' and 'Value_y' are to be specified or are they inbuilt keywords? Thanks for the help.

            – Nivi
            Mar 8 at 14:30






          • 1





            Got it. Thanks!

            – Nivi
            Mar 8 at 14:46






          • 1





            @Nivi - It is index and columns names created from columns names after crosstab

            – jezrael
            Mar 8 at 14:46















          3














          Use merge with cross join by ID column with crosstab and DataFrame.rename_axis for remove index and columns names:



          df = pd.merge(df, df, on='ID')

          df = pd.crosstab(df['Value_x'], df['Value_y']).rename_axis(None).rename_axis(None, axis=1)
          print (df)
          A B C
          A 1 1 1
          B 1 2 2
          C 1 2 2





          share|improve this answer




















          • 1





            'Value_x' and 'Value_y' are to be specified or are they inbuilt keywords? Thanks for the help.

            – Nivi
            Mar 8 at 14:30






          • 1





            Got it. Thanks!

            – Nivi
            Mar 8 at 14:46






          • 1





            @Nivi - It is index and columns names created from columns names after crosstab

            – jezrael
            Mar 8 at 14:46













          3












          3








          3







          Use merge with cross join by ID column with crosstab and DataFrame.rename_axis for remove index and columns names:



          df = pd.merge(df, df, on='ID')

          df = pd.crosstab(df['Value_x'], df['Value_y']).rename_axis(None).rename_axis(None, axis=1)
          print (df)
          A B C
          A 1 1 1
          B 1 2 2
          C 1 2 2





          share|improve this answer















          Use merge with cross join by ID column with crosstab and DataFrame.rename_axis for remove index and columns names:



          df = pd.merge(df, df, on='ID')

          df = pd.crosstab(df['Value_x'], df['Value_y']).rename_axis(None).rename_axis(None, axis=1)
          print (df)
          A B C
          A 1 1 1
          B 1 2 2
          C 1 2 2






          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Mar 8 at 14:30

























          answered Mar 8 at 14:28









          jezraeljezrael

          352k26317391




          352k26317391







          • 1





            'Value_x' and 'Value_y' are to be specified or are they inbuilt keywords? Thanks for the help.

            – Nivi
            Mar 8 at 14:30






          • 1





            Got it. Thanks!

            – Nivi
            Mar 8 at 14:46






          • 1





            @Nivi - It is index and columns names created from columns names after crosstab

            – jezrael
            Mar 8 at 14:46












          • 1





            'Value_x' and 'Value_y' are to be specified or are they inbuilt keywords? Thanks for the help.

            – Nivi
            Mar 8 at 14:30






          • 1





            Got it. Thanks!

            – Nivi
            Mar 8 at 14:46






          • 1





            @Nivi - It is index and columns names created from columns names after crosstab

            – jezrael
            Mar 8 at 14:46







          1




          1





          'Value_x' and 'Value_y' are to be specified or are they inbuilt keywords? Thanks for the help.

          – Nivi
          Mar 8 at 14:30





          'Value_x' and 'Value_y' are to be specified or are they inbuilt keywords? Thanks for the help.

          – Nivi
          Mar 8 at 14:30




          1




          1





          Got it. Thanks!

          – Nivi
          Mar 8 at 14:46





          Got it. Thanks!

          – Nivi
          Mar 8 at 14:46




          1




          1





          @Nivi - It is index and columns names created from columns names after crosstab

          – jezrael
          Mar 8 at 14:46





          @Nivi - It is index and columns names created from columns names after crosstab

          – jezrael
          Mar 8 at 14:46



















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