Formula Question: What is the formula to find how many duplicates I have in my table of data. e.g Sally, Sally, Sally, Tom, Tom, Ben. Answer by formula Sally 3, Tom 2, Ben 1

Question

Example of Data:
A1
2222222345
2222222345
2222222345
2222222345
2222222346
2222222346
2222222347
2222222347
2222222347
2222222347
2222222347
2222222347
Examplae of answer I would like the formula to provide:
I also can not manually type coullum A I need the formula to auto full that aswel. As there is to much data.
A2
B2
2222222345
4
2222222346
1
2222222347
6

Answer 1

Hi Jessica,
Here's my take on it, using the sample data in your original post, and using the same solution with the names in your question.
In the Data table, column A contains the list of numbers in your original post. I've rearranged them in random order to demonstrate that the order of entry does not matter for this method.
Data::Column B contains the names in your question, each assigned to one of the numbers in the body of your post.
Column C contains an index showing the first occurrence of each distinct number in Column A. This index is used to fill both columns in the Summary by Number table.
Column D contains an index showing the first occurrence of each distinct name in Column Bt. This index is used to fill both columns in the Summary by Number table.
Both formulas are the same, except for the columns referenced (highlighted in the second formula below).
Formula: Data::C2: =IF(COUNTIF($A$2:A2,A2)=1,MAX(C$1:C1)+1,"")
Formula: Data::D2: =IF(COUNTIF($B$2:B2,B2)=1,MAX(D$1:D1)+1,"")
Both formulas require that row 1 be a Header Row, and that the contents of C1 (and D1) be Text, nothing, or a zero. Both formulas are filled to the end of their respective columns.
Summary by Number contains two formulas.
A2: =IF((ROW()-1)>MAX(Data :: $C),"",LOOKUP(ROW()-1,Data :: $C,Data :: $A))
B2: =IF(LEN(A2)>0,COUNTIF(Data :: A,A2),"")
Both are filled down to the end of their respective columns.
The first formula checks if its row number minus 1 is greater than the maximum value in the index column. If that is TRUE, there are no more values to look up, and the formula returns an empty string (which appears 'blank'). If it is FALSE, the LOOKUP the value in Data::column A corresponding to the value of ROW()-1 in Data::column C.
The second formula checks the LENgth of the entry in the column to its left. If the length is greater that 0 characters, there is a countable value in the cell, and the formula passes control to COUNTIF, which counts the number of times that value is found in Data::column A. If the length of the value in the cell to the left is zero, then the cell contains an empty string, and the formula passes control to the part after the last comma, which enters an empty string in the cell containing the formula.
The formulas in Summary by Name are identical to these except for the (bolded) references. These are incremented to the right; C -> D, and A -> B to match the Data:: columns containing the names and the names index.
Regards,
Barry