I'm very new to filemaker and looking to set up a data collection system for a research project.
I have a table, FLOW_RECORDS, in which I am creating a new record for each time I collect data at each of many sampling sites (referred to by "Site_ID"). These records are timestamped, and I will be visiting each Site_ID approximately every day. In order to calculate flow rates, I need to know how much time has elapsed between records for a given sample site. I have created a field called "time_elapsed" where I am trying to calculate the difference between the automatically generated timestamp and the previous timestamp only for the matching Site_ID. I am having trouble determining what function I should use in the calculation of time_elapsed in order to look only at a subset of my table with matching Site_ID to the current record. My guess was using LookupNext(Timestamp;lower) but I haven't managed to delimit by Site_ID. Am I on the right track? Any ideas for another function which may solve my problem?