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*Subject*: [netCDF #HLX-917795]: a question about variables with one or more unlimited dimensions*Date*: Tue, 07 Feb 2012 12:17:01 -0700

ok, Given your example, at any point in time, the three unlimited dimensions will have some defined size. The total number of elements in the DATA array will be the crossproduct of the sizes of the three dimensions: i.e. |obs| * |parts| * |events| The critical point is that the size of, for example, events is independent of obs and parts. That is the sizeof the subslice DATA(x,y) is independent of x and y. So to your questions: (1) how many observations exist in the particular instance of the variable: DATA A: |obs| * |parts| * |events| (2) for each observation in DATA, how many parts were written for that observation A: |parts| * |events| although some of these probably are fill values. (3) for each part of a specific observation in DATA, how many events were written A: |events| again some will be fill values. Lets take a simpler case of an integer array A(X,Y), where X and Y are unlimited. Suppose A is initially as follows 1 10 11 12 This means that |X| = 2 and |Y| = 2 Suppose we insert the value 17 (using nc_put_vara) at A(2,0) We will then have 1 10 11 12 17 _ where _ indicates the use of a fill value, which is a default value for the type, integer in this case. Note the |Y| =2 still holds. Now let us insert the value 23 at A(1,2), We will get 1 10 _ 11 12 23 17 _ _ |X| = 3 and |Y|=3 still holds even though you only added a single value at A(1,2). I should note that at least for netcdf-4, those extra fill values do not necessarily take up space on disk. personally, I do not like multiple unlimited dimensions because of this rather non-intuitive semantics. An alternative uses variable length types (vlen). So you might define the following types: types: int(*) events_t; events_t(*) parts_t; and either this: dimensions: U=UNLIMITED; variables: parts_t A(U); or types: parts_t(*) obs_t; variables: obs_t A; Personally, I prefer the use of a the unlimited dimension here because it is easier to access. =Dennis Heimbigner Unidata Ticket Details =================== Ticket ID: HLX-917795 Department: Support netCDF Priority: Normal Status: Closed

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