I have a dataset with variable: year quarter month ID. year is from 1990 to 2000 quarter is 1, 2, 3, 4 month is 1,2,3,,,,,12 1) only save ID that appears in every year (it should have at leat two observation every year(that is, as long as it has observations for any two months in each year, then it will be saved), from 1990 to 2000); With this condition, would expect to save obs for: aa, bb, cc, ee 2) only save ID that appears in every quarter (it should have at leat one observation in each quarter within each year, from 1990 Q1 to 2000 Q4); With this condition, would expect to save obs for: aa, bb, ee 3) only save ID that appears in every month (it should have at leat one observation in every month within each year,, from 1990 Jan to 2000 Dec). With this condition, would expect to save obs for: aa, bb Thanks! attached is the sample data.
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