Reshaping multiple sets of measurement columns (wide format) into single columns (long format)
问题 I have a dataframe in a wide format, with repeated measurements taken within different date ranges. In my example there are three different periods, all with their corresponding values. E.g. the first measurement ( Value1 ) was measured in the period from DateRange1Start to DateRange1End : ID DateRange1Start DateRange1End Value1 DateRange2Start DateRange2End Value2 DateRange3Start DateRange3End Value3 1 1/1/90 3/1/90 4.4 4/5/91 6/7/91 6.2 5/5/95 6/6/96 3.3 I\'m looking to reshape the data to