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Re: [netcdfgroup] arrays of fixed-length strings


Jeff Whitaker wrote:

Ed Hartnett wrote:

Jeff Whitaker <jswhit@xxxxxxxxxxx> writes:


In netcdf-4.0, I don't see how to create variables which are arrays of
strings with length > 1.  I see how to create arrays of
single-characters, and arrays of variable-length strings, but not
strings of a specified length.

Am I missing something, or is this not supported by HDF5?


Howdy Jeff!

Strings are variable length by their nature.

How about a two dimensional array of NC_CHAR?

Thanks,

Ed
Ed: I use arrays of fixed length strings, padded with spaces, quite a bit. This simplifies the memory management issues associated with arrays of variable length strings (which have no counterpart in Fortran 90/95, although they are allowed in Fortran 2003). Below is an excerpt from my previous reply which explains why I don't like using 2-D arrays of characters to represent 1-D arrays of fixed-length strings: 
Russ: I realize you can use a array of shape ndim,8 to store an array of 
ndim 8 character strings.  Thats the way I've done it with netcdf-3 - it 
just feels clunky.  A typical use case for me is station data, where you 
want to store the name of the station. I end up the with an array of 
characters shaped (nstations,ncars) -  in fortran I read it into an  
(nstations,nchars) character(len=1) array (after first finding out what 
both nstations and nchars are), then reshape it into a (nstations) 
character(len=nchars) array.  I'd rather just read it into a 
character(len=nchars) array straight off.  Not a show stopper for sure, 
but it would be more convenient.  I realize that specifying the data 
type would be tricky,  instead of NC_CHAR, do you have a bunch of new 
types NC_CHAR1, NC_CHAR2, ... NC_CHAR120?  Or a new function datatype = 
nc_set_chartype(nchars)?  However, I bet it would get used a lot more 
than the esoteric datatypes you have in netcdf-4 already (enums and 
opaque for example).

Hi Jeff:

Suppose we stuck with fixed length char arrays for this case, but added a 
convenience method in the API that did the work for you. What would that 
convenience method look like?

John







   
  
   







   
 
   

    
    
     
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