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Calculation involving differences between timestamps

Question asked by broccolus on Nov 23, 2015
Latest reply on Nov 27, 2015 by broccolus

Hi Everybody



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?