How to represent packed variable statistics (e.g., valid_range, mean)?

• To: NetCDF mailing list <netcdfgroup@xxxxxxxxxxxxxxxx>
• Subject: How to represent packed variable statistics (e.g., valid_range, mean)?
• From: "Mark A Ohrenschall" <Mark.A.Ohrenschall@xxxxxxxx>
• Date: Wed, 02 Oct 2002 09:27:59 -0600

Hello,

In the case of a packed variable (in which scale_factor and add_offset
are used) both the COARDS and CF conventions indicate that missing_value
and _FillValue should be likewise packed:

COARDS: "In cases where the data variable is packed via the scale_value
attribute this implies that the missing_value flag is likewise packed."
CF: "The missing values of a variable with scale_factor and/or
add_offset attributes (see section 8.1) are interpreted relative to the
variable's external values, i.e., the values stored in the netCDF file."

I'm assuming that for the sake of consistency, this means that all
statistical variable attributes should be packed as well, e.g.,
valid_range and actual_range, as well as mean and standard_deviation. Is
this true?

So for example, if I have real world data values for temperature between
-1.6 and 31.4 and I'm applying a scale_factor of 0.1 then I would say
the valid_range is -16, 314 and the mean is 116 (not 11.6)?

Thanks,

Mark

• Follow-Ups:
  • Re: How to represent packed variable statistics (e.g., valid_range,
    • From: Timothy Hume
  • Re: How to represent packed variable statistics (e.g., valid_range, mean)?
    • From: John Caron