Use the formula =INT(A1)=A1, where "A1" indicates the cell to pull data from, then once you've set up the formula on the desired column select Data > Filter and choose how to filter the data. After that, choose either TRUE of FALSE to set the indicator for the given data (whole number or decimal), then select OK to finalize. You should then see TRUE and FALSE displayed next to each of the cells with numbers in them, to indicate those with and without decimals (dependent on which value you chose to indicate which).