DAX expression for a new calculated column counting all rows in the table with same value in column

[jsteinigen]

Hello! 

I can't figure out how to compare the value of the current cell in a column with the rest of the value of that column. What I mean is, I understand that the calculation for the new column is done one row at a time, iterating through the whole table, right? Therefore, I want to take the 3rd column in the 1st row and compare it to the 3rd column in all other rows and count the number of rows that contain the same value, then write that number in the new calculated column for the first row and move on to the next row until the table is done. But how do I address the first (n-th) row 3rd column cell to compare it to all other rows' 3rd column cells to count those that match?

index   random   3rd_column    new_calculated

   1         ...                 A                     4

   2         ...                 A                     4

   3         ...                 A                     4

   4         ...                 A                     4

   5         ...                 B                     2

   6         ...                 B                     2

   7         ...                 C                     3

   8         ...                 C                     3

   9         ...                 C                     3

   10       ...                 D                     1

Any help how to count the rows with the same value in 3rd_colum to write the value into new_column of that row with a DAX function would be appreciated. 

Cheers

Jens

[jsteinigen · Accepted solution]

Somehow I tend to answer my own questions here. I figured it out now: 

new_calculated = COUNTROWS(FILTER('current table', 
     (EARLIER('current table'[3rd_column]) = 'current table'[3rd_column])))