Hi Saurabh,suppose i want to calculate total heat content of global ocean in joules (a line plot) so how to get the global ocean area only such thatlet OHC=heat[z=0:700@ave,x=@ave,y=@ave] !! units are j/m^2 let TOHC=OHC*(global ocean area) !! units are j, TOHC=total OHCThat's a very roundabout approach. You first compute the area average and then multiply the area. But why? Look at the definition of area average:(area average) = (area integral) / (area)Ferret does this when you ask for area average. Now, you say you want to compute (area average) * (area), which is the area integral! which you can directly compute withx=<xrange>@DIN, y=<yreange>@DINIf you really, really want to compute the area, you can use this trick:(area) = integral dx dy= integral 1 dx dyThat is, you first define a function which is 1 in ocean and undefined on land:let mask = ifv somevariable then 1let area = mask[x=<xrange>@DIN, y=<yrange>@DIN]Read the manual about @DIN and IFV .Ryo