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#108: Defining a domain for a cell_method -----------------------------+---------------------------------------------- Reporter: markh | Owner: [email protected] Type: enhancement | Status: new Priority: medium | Milestone: Component: cf-conventions | Version: Resolution: | Keywords: -----------------------------+---------------------------------------------- Comment (by jonathan): Dear Mark I'd like to put forward a different argument in support of your preference, namely that if we relied on the dimension name alone it would have to be assumed that all variables with that dimension were auxiliaries of the field before collapse. That is not necessary so; some such variables might be irrelevant. Looking at the issue that way, it now seems to me is that what we need to record is the coordinates and auxiliary coordinates of the field before collapse. This information is more complete than you can record with `interval`. Here's a proposal for the new para along these lines: The original domain of the variable before the statistical operation was applied can be described completely using "`dimension:` ''dimname'' [''dimname'' ...]" and `coordinates:` ''varname'' [''varname'' ...]". The ''dimname''s are the names of the netCDF dimensions for the affected axes in the original domain. This syntax implies that any 1D variable whose name is ''dimname'' is a coordinate variable of the original domain. The ''varname''s are the names of auxiliary coordinate variables for the affected axes in the original domain. Before the statistical operation was carried out, these variables would have been named by the `coordinates` attribute of the original data variable. In addition, I think we would need to amend the opening para of 7.3.2 To indicate more precisely how the cell method was applied, extra information may optionally be included in parentheses () after the identification of the method. This information includes standardized and non-standardized parts. The possible standardized parts begin with `interval:`, `dimensions:` and `coordinates:`. To provide the typical interval between the original data values to which the method was applied, in the situation where the present data values are statistically representative of original data values which had a finer spacing, the syntax is ... and perhaps we might rename the section to a more general title. New requirements in the conformance document for sect 7.3.2: * The names listed after `dimensions:` must all be names of netCDF dimensions, which must not be dimensions of the data variable. * Any 1D variable whose name equals the name of one of the original dimensions is regarded as a coordinate variable of the original domain and therefore must be strictly monotonic (increasing or decreasing) and must not have the `_FillValue` or `missing_value` attributes. * If there is a `coordinates:` list for a `cell_methods` entry there must also be a `dimensions:` list for the same entry. * The names listed after `coordinates:` must all be names of netCDF variables. These variables are regarded as auxiliary coordinate variables of the original domain. They must not have as dimensions any of the dimensions to which the `cell_methods` entry applies. Their dimensions must be a subset of the other dimensions of the data variable and the original dimensions named by this `cell_methods` entry. In addition, any label variable will have a trailing dimension for the maximum string length. What do you think? Cheers Jonathan -- Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/108#comment:3> CF Metadata <http://cf-pcmdi.llnl.gov/> CF Metadata This message came from the CF Trac system. To unsubscribe, without unsubscribing to the regular cf-metadata list, send a message to "[email protected]" with "unsubscribe cf-metadata" in the body of your message.
