Excel: Fleshing out column data by another column ID - excel

Question

I have an excel file with multiple rows that have the same "Subject ID" with a column (Value A) that will always have the same value by subject ID (or be empty). Example:
╔══════════════════════════╗
║ | subject id | value A | ║
╠══════════════════════════╣
║ |:----------:|---------| ║
║ | 1 | A | ║
║ | 1 | A | ║
║ | 1 | | ║
║ | 1 | | ║
║ | 2 | | ║
║ | 2 | | ║
║ | 2 | B | ║
╚══════════════════════════╝
How can I in Excel create a formula that I can drag down the Value A column such that it gives all of the rows with the same subject ID the same value for Value A? There is no situation in my data in which there would be different values in the Value A column for a particular subject ID: it will either have a value or not.
For example, with this I want to make it so that all of the subjects with an ID of one get a Value A of "A", and for every record with a subject id of 2, I want it to receive a value of "B". Example:
╔══════════════════════════╗
║ | subject id | value A | ║
╠══════════════════════════╣
║ |:----------:|---------| ║
║ | 1 | A | ║
║ | 1 | A | ║
║ | 1 | A | ║
║ | 1 | A | ║
║ | 2 | B | ║
║ | 2 | B | ║
║ | 2 | B | ║
╚══════════════════════════╝

Answer 1

Use Char to convert the number to a char using the ASCII code.
Note, this will only work up to a value of 26, after that you run out of letters and will start getting brackets and other chars
=CHAR(A2+64)

Answer 2

Extending on Dan's solution, this solution should work on more than 26 different IDs
=IF(A1>26,CHAR(QUOTIENT(A1-1,26)+64),"") & CHAR(1+MOD(A1-1,26)+64)
Where A1 has the ID. this formulae gives in the below results
1 A
2 B
.
.
.
26 Z
27 AA
28 AB
29 AC
.
.
.
44 AR
45 AS
.
.
.
53 BA
54 BB
55 BC

Answer 3

Here are my results:
+------------+---------+----------------+
| subject id | value A | Formula result |
+------------+---------+----------------+
| 1 | | Hello |
| 1 | | Hello |
| 1 | Hello | Hello |
| 1 | | Hello |
| 1 | | Hello |
| 1 | | Hello |
| 2 | | B |
| 2 | B | B |
| 2 | B | B |
| 2 | | B |
| 2 | | B |
| 2 | B | B |
| 3 | | World |
| 3 | | World |
| 3 | World | World |
| 3 | | World |
| 3 | | World |
| 4 | | D |
| 4 | D | D |
| 4 | | D |
| 4 | | D |
+------------+---------+----------------+
I built a UDF for it the formula in C2 is =GetCode(A2,$A$2:$A$22,1) where the first parameter is the value to search for, the second is the range to search in and the last is the columns to offset to look for a result.
Code below:
Function GetCode(InputValue As String, SearchRange As Range, ColOffset As Long)
Dim TempVal As String, FirstFoundRow As Long, LastFoundRow As Long, X As Long
On Error Resume Next 'If not found the result will be null
TempVal = Null
If WorksheetFunction.CountIf(SearchRange, InputValue) > 0 Then
FirstFoundRow = SearchRange.Find(InputValue).Row 'Determine the rows to check
LastFoundRow = SearchRange.Find(InputValue, , , , , xlPrevious).Row 'Find the last row, no need to test after that
For X = FirstFoundRow To LastFoundRow 'Loop the checking rows
TempVal = SearchRange.Cells(X, ColOffset + 1).Text 'Assign the value of the offset column for the tested row
If TempVal <> "" Then Exit For 'Quit the loop if it has found the answer
Next
End If
GetCode = TempVal
End Function
Assumption:
subject ID is sorted. If it is not it will give the WRONG results, it would be simple enough for you to modify the code to search through instances in none contiguous data.
note: Please try to format your question with a little more key detail, all the previous answers made the same assumption I did (When you have 1 - A, 2 - B as your sample data it's an easy thing to assume) and also with reference to my above assumption, I had to make the assumption of sorted data as you didn't tell us.
A none code option would have been to take a copy, remove dupes, sort on col B to remove the blanks then use a VLOOKUP formula against the freshly created matrix.