pandas filling nans by mean of before and after non-nan values












11















I would like to fill df's nan with an average of adjacent elements.



Consider a dataframe:



df = pd.DataFrame({'val': [1,np.nan, 4, 5, np.nan, 10, 1,2,5, np.nan, np.nan, 9]})
val
0 1.0
1 NaN
2 4.0
3 5.0
4 NaN
5 10.0
6 1.0
7 2.0
8 5.0
9 NaN
10 NaN
11 9.0


My desired output is:



    val
0 1.0
1 2.5
2 4.0
3 5.0
4 7.5
5 10.0
6 1.0
7 2.0
8 5.0
9 7.0 <<< deadend
10 7.0 <<< deadend
11 9.0


I've looked into other solutions such as Fill cell containing NaN with average of value before and after, but this won't work in case of two or more consecutive np.nans.



Any help is greatly appreciated!










share|improve this question



























    11















    I would like to fill df's nan with an average of adjacent elements.



    Consider a dataframe:



    df = pd.DataFrame({'val': [1,np.nan, 4, 5, np.nan, 10, 1,2,5, np.nan, np.nan, 9]})
    val
    0 1.0
    1 NaN
    2 4.0
    3 5.0
    4 NaN
    5 10.0
    6 1.0
    7 2.0
    8 5.0
    9 NaN
    10 NaN
    11 9.0


    My desired output is:



        val
    0 1.0
    1 2.5
    2 4.0
    3 5.0
    4 7.5
    5 10.0
    6 1.0
    7 2.0
    8 5.0
    9 7.0 <<< deadend
    10 7.0 <<< deadend
    11 9.0


    I've looked into other solutions such as Fill cell containing NaN with average of value before and after, but this won't work in case of two or more consecutive np.nans.



    Any help is greatly appreciated!










    share|improve this question

























      11












      11








      11


      1






      I would like to fill df's nan with an average of adjacent elements.



      Consider a dataframe:



      df = pd.DataFrame({'val': [1,np.nan, 4, 5, np.nan, 10, 1,2,5, np.nan, np.nan, 9]})
      val
      0 1.0
      1 NaN
      2 4.0
      3 5.0
      4 NaN
      5 10.0
      6 1.0
      7 2.0
      8 5.0
      9 NaN
      10 NaN
      11 9.0


      My desired output is:



          val
      0 1.0
      1 2.5
      2 4.0
      3 5.0
      4 7.5
      5 10.0
      6 1.0
      7 2.0
      8 5.0
      9 7.0 <<< deadend
      10 7.0 <<< deadend
      11 9.0


      I've looked into other solutions such as Fill cell containing NaN with average of value before and after, but this won't work in case of two or more consecutive np.nans.



      Any help is greatly appreciated!










      share|improve this question














      I would like to fill df's nan with an average of adjacent elements.



      Consider a dataframe:



      df = pd.DataFrame({'val': [1,np.nan, 4, 5, np.nan, 10, 1,2,5, np.nan, np.nan, 9]})
      val
      0 1.0
      1 NaN
      2 4.0
      3 5.0
      4 NaN
      5 10.0
      6 1.0
      7 2.0
      8 5.0
      9 NaN
      10 NaN
      11 9.0


      My desired output is:



          val
      0 1.0
      1 2.5
      2 4.0
      3 5.0
      4 7.5
      5 10.0
      6 1.0
      7 2.0
      8 5.0
      9 7.0 <<< deadend
      10 7.0 <<< deadend
      11 9.0


      I've looked into other solutions such as Fill cell containing NaN with average of value before and after, but this won't work in case of two or more consecutive np.nans.



      Any help is greatly appreciated!







      python pandas






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 47 mins ago









      ChrisChris

      1,206214




      1,206214
























          1 Answer
          1






          active

          oldest

          votes


















          14














          Use ffill + bfill and divide by 2:



          df = (df.ffill()+df.bfill())/2

          print(df)
          val
          0 1.0
          1 2.5
          2 4.0
          3 5.0
          4 7.5
          5 10.0
          6 1.0
          7 2.0
          8 5.0
          9 7.0
          10 7.0
          11 9.0


          EDIT : If 1st and last element contains NaN then use (Dark
          suggestion):



          df = pd.DataFrame({'val':[np.nan,1,np.nan, 4, 5, np.nan, 
          10, 1,2,5, np.nan, np.nan, 9,np.nan,]})
          df = (df.ffill()+df.bfill())/2
          df = df.bfill().ffill()

          print(df)
          val
          0 1.0
          1 1.0
          2 2.5
          3 4.0
          4 5.0
          5 7.5
          6 10.0
          7 1.0
          8 2.0
          9 5.0
          10 7.0
          11 7.0
          12 9.0
          13 9.0





          share|improve this answer





















          • 3





            That is just brilliant. Thanks a ton :)

            – Chris
            39 mins ago











          • @Chris Glad to help.

            – Sandeep Kadapa
            34 mins ago






          • 3





            If first and last elements are nan. Then use df.bfill().ffill() after using the above solution.

            – Dark
            19 mins ago











          • @anon01 Good point

            – Chris
            16 mins ago











          • @Dark Great suggestion :) Thanks for the insight

            – Chris
            16 mins ago











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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          14














          Use ffill + bfill and divide by 2:



          df = (df.ffill()+df.bfill())/2

          print(df)
          val
          0 1.0
          1 2.5
          2 4.0
          3 5.0
          4 7.5
          5 10.0
          6 1.0
          7 2.0
          8 5.0
          9 7.0
          10 7.0
          11 9.0


          EDIT : If 1st and last element contains NaN then use (Dark
          suggestion):



          df = pd.DataFrame({'val':[np.nan,1,np.nan, 4, 5, np.nan, 
          10, 1,2,5, np.nan, np.nan, 9,np.nan,]})
          df = (df.ffill()+df.bfill())/2
          df = df.bfill().ffill()

          print(df)
          val
          0 1.0
          1 1.0
          2 2.5
          3 4.0
          4 5.0
          5 7.5
          6 10.0
          7 1.0
          8 2.0
          9 5.0
          10 7.0
          11 7.0
          12 9.0
          13 9.0





          share|improve this answer





















          • 3





            That is just brilliant. Thanks a ton :)

            – Chris
            39 mins ago











          • @Chris Glad to help.

            – Sandeep Kadapa
            34 mins ago






          • 3





            If first and last elements are nan. Then use df.bfill().ffill() after using the above solution.

            – Dark
            19 mins ago











          • @anon01 Good point

            – Chris
            16 mins ago











          • @Dark Great suggestion :) Thanks for the insight

            – Chris
            16 mins ago
















          14














          Use ffill + bfill and divide by 2:



          df = (df.ffill()+df.bfill())/2

          print(df)
          val
          0 1.0
          1 2.5
          2 4.0
          3 5.0
          4 7.5
          5 10.0
          6 1.0
          7 2.0
          8 5.0
          9 7.0
          10 7.0
          11 9.0


          EDIT : If 1st and last element contains NaN then use (Dark
          suggestion):



          df = pd.DataFrame({'val':[np.nan,1,np.nan, 4, 5, np.nan, 
          10, 1,2,5, np.nan, np.nan, 9,np.nan,]})
          df = (df.ffill()+df.bfill())/2
          df = df.bfill().ffill()

          print(df)
          val
          0 1.0
          1 1.0
          2 2.5
          3 4.0
          4 5.0
          5 7.5
          6 10.0
          7 1.0
          8 2.0
          9 5.0
          10 7.0
          11 7.0
          12 9.0
          13 9.0





          share|improve this answer





















          • 3





            That is just brilliant. Thanks a ton :)

            – Chris
            39 mins ago











          • @Chris Glad to help.

            – Sandeep Kadapa
            34 mins ago






          • 3





            If first and last elements are nan. Then use df.bfill().ffill() after using the above solution.

            – Dark
            19 mins ago











          • @anon01 Good point

            – Chris
            16 mins ago











          • @Dark Great suggestion :) Thanks for the insight

            – Chris
            16 mins ago














          14












          14








          14







          Use ffill + bfill and divide by 2:



          df = (df.ffill()+df.bfill())/2

          print(df)
          val
          0 1.0
          1 2.5
          2 4.0
          3 5.0
          4 7.5
          5 10.0
          6 1.0
          7 2.0
          8 5.0
          9 7.0
          10 7.0
          11 9.0


          EDIT : If 1st and last element contains NaN then use (Dark
          suggestion):



          df = pd.DataFrame({'val':[np.nan,1,np.nan, 4, 5, np.nan, 
          10, 1,2,5, np.nan, np.nan, 9,np.nan,]})
          df = (df.ffill()+df.bfill())/2
          df = df.bfill().ffill()

          print(df)
          val
          0 1.0
          1 1.0
          2 2.5
          3 4.0
          4 5.0
          5 7.5
          6 10.0
          7 1.0
          8 2.0
          9 5.0
          10 7.0
          11 7.0
          12 9.0
          13 9.0





          share|improve this answer















          Use ffill + bfill and divide by 2:



          df = (df.ffill()+df.bfill())/2

          print(df)
          val
          0 1.0
          1 2.5
          2 4.0
          3 5.0
          4 7.5
          5 10.0
          6 1.0
          7 2.0
          8 5.0
          9 7.0
          10 7.0
          11 9.0


          EDIT : If 1st and last element contains NaN then use (Dark
          suggestion):



          df = pd.DataFrame({'val':[np.nan,1,np.nan, 4, 5, np.nan, 
          10, 1,2,5, np.nan, np.nan, 9,np.nan,]})
          df = (df.ffill()+df.bfill())/2
          df = df.bfill().ffill()

          print(df)
          val
          0 1.0
          1 1.0
          2 2.5
          3 4.0
          4 5.0
          5 7.5
          6 10.0
          7 1.0
          8 2.0
          9 5.0
          10 7.0
          11 7.0
          12 9.0
          13 9.0






          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 15 mins ago

























          answered 41 mins ago









          Sandeep KadapaSandeep Kadapa

          6,873630




          6,873630








          • 3





            That is just brilliant. Thanks a ton :)

            – Chris
            39 mins ago











          • @Chris Glad to help.

            – Sandeep Kadapa
            34 mins ago






          • 3





            If first and last elements are nan. Then use df.bfill().ffill() after using the above solution.

            – Dark
            19 mins ago











          • @anon01 Good point

            – Chris
            16 mins ago











          • @Dark Great suggestion :) Thanks for the insight

            – Chris
            16 mins ago














          • 3





            That is just brilliant. Thanks a ton :)

            – Chris
            39 mins ago











          • @Chris Glad to help.

            – Sandeep Kadapa
            34 mins ago






          • 3





            If first and last elements are nan. Then use df.bfill().ffill() after using the above solution.

            – Dark
            19 mins ago











          • @anon01 Good point

            – Chris
            16 mins ago











          • @Dark Great suggestion :) Thanks for the insight

            – Chris
            16 mins ago








          3




          3





          That is just brilliant. Thanks a ton :)

          – Chris
          39 mins ago





          That is just brilliant. Thanks a ton :)

          – Chris
          39 mins ago













          @Chris Glad to help.

          – Sandeep Kadapa
          34 mins ago





          @Chris Glad to help.

          – Sandeep Kadapa
          34 mins ago




          3




          3





          If first and last elements are nan. Then use df.bfill().ffill() after using the above solution.

          – Dark
          19 mins ago





          If first and last elements are nan. Then use df.bfill().ffill() after using the above solution.

          – Dark
          19 mins ago













          @anon01 Good point

          – Chris
          16 mins ago





          @anon01 Good point

          – Chris
          16 mins ago













          @Dark Great suggestion :) Thanks for the insight

          – Chris
          16 mins ago





          @Dark Great suggestion :) Thanks for the insight

          – Chris
          16 mins ago


















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