Excel 2010.
Never had this occur previously:
I copied and pasted the data in this workbook from another workbook.
I select "Filter" for a column (the following happens regardless of which column I select in this worksheet).
E.g., the cells in the column state either "Y" or "N".
I select only "Y" in the filter.
Every cell in that column changes to "Y".
Anotherwords, instead of only showing me the "Y"s which were there and filtering out the "N"s, it changes all the "N"s to "Y"s and the pre-existing "Y"s remain such.
If I go back to the filter having everything checked ("Select all"), all the cells go back to having the correct data again.
??
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