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Paul, I belatedly read the "Adding two different 4d grids" thread on the IDV Users list. I have been using your formula to add 4D fields that physically do not make sense (e.g., geopotential height and relative humidity) without problems in the IDV. The IDV/Jython seem to be handling the unit incompatibility without problems for the fields I am experimenting with. Again, specific examples of what you are trying to achieve may be helpful. Best, Unidata IDV Support > Paul, > > I tried your formula and was able to make it work in my scenario so we are > going to have to find out a bit more about what you are trying to achieve. > Where is the data coming from? What fields are you trying to add? You can > upload a data file for us to examine at > http://motherlode.ucar.edu/repository/alias/idvupload. > > Best Wishes, > > Unidata IDV Support > > > > Full Name: Paul Graham > > Email Address: address@hidden > > Organization: Weathersim > > Package Version: 4.0u1 build date:2013-03-29 18:10 UTC > > Operating System: Mac OS X > > Hardware: Java: home: > > /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home version: > > 1.6.0_51 j3d:1.5.2 fcs (build4) > > Description of problem: > > > > When attempting to add two different fields in IDV using the following > > simple Jython method: > > > > def simpleAdd(F1,F2): > > res = add(noUnit(F1),noUnit(F2)) > > return res > > > > The following error occurs: > > > > "Making the widget component > > java.lang.NullPointerException" > > > > > > > > ****************** > > Stack trace: > > java.lang.NullPointerException > > at > > ucar.unidata.idv.control.GridDisplayControl.getDataRangeInColorUnits(GridDisplayControl.java:264) > > at > > ucar.unidata.idv.control.GridDisplayControl.getInitialRange(GridDisplayControl.java:233) > > at > > ucar.unidata.idv.control.DisplayControlImpl.getRange(DisplayControlImpl.java:10001) > > at > > ucar.unidata.idv.control.DisplayControlImpl.getRangeForColorTable(DisplayControlImpl.java:10029) > > at > > ucar.unidata.idv.control.DisplayControlImpl.getControlWidgets(DisplayControlImpl.java:7588) > > at > > ucar.unidata.idv.control.PlanViewControl.getControlWidgets(PlanViewControl.java:1543) > > at > > ucar.unidata.idv.control.ContourPlanViewControl.getControlWidgets(ContourPlanViewControl.java:218) > > at > > ucar.unidata.idv.control.DisplayControlImpl.doMakeWidgetComponent(DisplayControlImpl.java:7483) > > at > > ucar.unidata.idv.control.PlanViewControl.doMakeContents(PlanViewControl.java:1498) > > at > > ucar.unidata.idv.control.DisplayControlImpl.doMakeWindow(DisplayControlImpl.java:4266) > > at > > ucar.unidata.idv.control.DisplayControlImpl.init(DisplayControlImpl.java:1141) > > at > > ucar.unidata.idv.ControlDescriptor.initControl(ControlDescriptor.java:986) > > at ucar.unidata.idv.ControlDescriptor$1.run(ControlDescriptor.java:911) > > at ucar.unidata.util.Misc$3.run(Misc.java:1249) > > > > > > > Ticket Details =================== Ticket ID: DIZ-849299 Department: Support IDV Priority: Normal Status: Open