Re: arrays of fixed-length strings

[Jeff Whitaker <jswhit@xxxxxxxxxxx>]

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).


-Jeff

--
Jeffrey S. Whitaker         Phone  : (303)497-6313
Meteorologist               FAX    : (303)497-6449
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