Hi Riccardo, Sorry for the delay in getting back to you. This just slipped through the cracks of our support box. > Description of problem: I STARTED USING IDL TODAY. WHAT I'D LIKE TO DO IS > VERY SIMPLE: I HAVE A GRIB FILE WITH CUMULATED PRECIPITATIONS FROM ECMWF > OPERATIONAL MODEL, AND I WANT TO MAKE A "SIMPLE TIME DIFFERENCE" IN ORDER TO > SEE THE CUMULATED VALUE IN 12 HOURS: T24-T12, T36-T24 AND SO ON. IT APPEARS A > SMALL WINDOWS REQUESTING "TIME1" AND "TIME2", BUT I DON'T UNDERSTAND WHICH > VALUES I HAVE TO PUT INSIDE. THANK YOU VERY MUCH IN ADVANCE. RICCARDO > The latest version of the IDV has a formula Formulas->Grids->Time Steps->Time step difference that takes a grid field and does a difference so that: Data(T) = Data(T)-Data(T-1) Note - the -1 offset is the index of the time, e.g., -3 is not -3 hours but is the time 3 time stpes prior. This is not the absolute time. One can also specify an arbitrary (index) offset using another formula. Attached is a plugin (install it through the Tools->Plugin Manager dialog under its File menu). This has a formula that prompts the user or an offset. It also has a fix to a problem in our released jython library (it call a routine fixedtimeStepDifference not the normal (and broken) timeStepDifference). -Jeff Ticket Details =================== Ticket ID: ELV-470278 Department: Support IDV Priority: Critical Status: Closed
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timestepdifference.jar
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