Average select values in column based on helper column

[westend9876]

I have a list of values in Column A
Column B is a helper column that groups the values together from Column A using numbers
Column C is the results column that returns the average for each group of values in Column A

To note, Columns A and B will be appended with new data daily.

I need a formula in Column C to return the average of the grouped values from Column A.
An example spreadsheet is attached with the correct results highlighted in Column C.

 

[bosco_yip]

In D2 formula copied down :

=IF(ROW(A1)<=MAX(B:B),AVERAGEIFS(A:A,B:B,ROW(A1)),"")

Or,

=IF(ROW(A1)<=MAX(B:B),AVERAGEIF(B:B,ROW(A1),A:A),"")

 

[Peter Bartholomew]

I would recommend using Tables (introduce to Excel in 2007) to hold dynamic source data.
The best formula would require Excel 365

= AVERAGEIFS(Table1[Values],
    Table1[Helper], UNIQUE(Table1[Helper]))

but as long as you can generate a list of distinct helpers the AVERAGEIFS will respond dynamically.
CSE or relative referencing would work for older versions.