Werner,
Sorry, I missed the attached file and program! They are very helpful. By
the way, I learned about transient datatypes. :) Your solution seems to
me a bit more complicated than creating a compound attribute. However,
it is a matter of taste and maybe it is because I did not used to
transient datatypes.
Anton
> Anton,
>
> there are no groups in this file. It only contains as single data set of five
> elements which is build from a compound datatype of type struct { double t,x;
> }.
>
> This compound datatype has two attributes, called "t" which is of type
> "seconds"
> and another attribute "x" which is of type "meter"; both "seconds" and "meter"
> are of type "double".
>
> I'm more used to h5ls, but the hdf5 file was attached, so you can give h5dump
> a try on it (I don't have h5dump installed here at the moment for 1.8).
>
> For the given scenario, to find the units of a dataset's compound member,
> you would need to look at an attribute of the same name as the compound
> member,
> and this one would be of the type of the respective unit. In the example below
> the value of this attribute is zero, it's not really used, but it could e.g.
> have some scaling value, for instance 1000 to tell that the x-values of this
> dataset is given in kilometres.
>
> Werner
>
>
> On Thu, 18 Mar 2010 13:30:15 -0500, Anton Kulchitsky <[email protected]>
> wrote:
>
>> Werner,
>>
>> I did not understand exactly what is this. Does it mean creating some
>> additional groups with names of units and making links to the data?
>>
>> I worry it is too complicated especially for those who never saw the
>> data before and needs just take a quick look into the file they received?
>> Maybe I missed the point. Maybe h5dump would show more details?
>>
>> Anton
>>
>>> Anton,
>>>
>>> would something like the following do? HDF5 file and source code attached.
>>>
>>> It's not as elegant as the forthcoming method to have attributes directly
>>> at the compound type's members, but is some kind of workaround with the
>>> existing methods.
>>>
>>> Werner
>>>
>>>
>>> h5ls -rvd test.h5
>>> Opened "test.h5" with sec2 driver.
>>> / Group
>>> Location: 1:96
>>> Links: 1
>>> /data Dataset {5/5}
>>> Location: 1:1504
>>> Links: 1
>>> Storage: 80 logical bytes, 80 allocated bytes, 100.00% utilization
>>> Type: shared-1:1224 struct {
>>> "t" +0 native double
>>> "x" +8 native double
>>> } 16 bytes
>>> Data:
>>> (0) {1, 2}, {3, 4}, {1, 4}, {1, 5}, {5, 0}
>>> /meter Type
>>> Location: 1:800
>>> Links: 2
>>> Type: shared-1:800 native double
>>> /seconds Type
>>> Location: 1:1176
>>> Links: 2
>>> Type: shared-1:1176 native double
>>> /spatiotemporal Type
>>> Attribute: t {1}
>>> Type: shared-1:1176 native double
>>> Data: 0
>>> Attribute: x {1}
>>> Type: shared-1:800 native double
>>> Data: 0
>>> Location: 1:1224
>>> Links: 2
>>> Type: shared-1:1224 struct {
>>> "t" +0 native double
>>> "x" +8 native double
>>> } 16 bytes
>>>
>>>
>>>
>>> On Thu, 18 Mar 2010 11:40:10 -0500, Anton Kulchitsky <[email protected]>
>>> wrote:
>>>
>>>> Francesc,
>>>>
>>>> I think this is a really nice and elegant solution. Honestly, I am still
>>>> thinking of attributes as of simple strings. Now I see the advantage to
>>>> use other types. Thank you!
>>>>
>>>> I see just another problem with this though. Actually, what I really
>>>> want is attributes for the types, not the data! When attributes are
>>>> associated with data, this compound attribute need to be written every
>>>> time when I write data of this type. However, what I really need for
>>>> compound type are attributes of the type. Indeed, once fields are
>>>> described there is no need to repeat this every time I write the data
>>>> into a file.
>>>>
>>>> Anton
>>>>
>>>>> A Tuesday 16 March 2010 23:56:38 Anton Kulchitsky escrigué:
>>>>>> I would like to specify physical units and long names for every field of
>>>>>> a compound object. I have an array of particles. Each particle is
>>>>>> specified as a C structure with many fields associated with it. I would
>>>>>> like to have an attribute for every field. However, when I create a
>>>>>> compound object, I am not able to specify an attribute for a
>>>>>> field. I am wondering if anyone has similar problem?
>>>>>
>>>>> An elegant solution for this would be to write a compound type attribute,
>>>>> with
>>>>> the first field specifying the field to be described and the others with
>>>>> complementary info. For example, if you have a table with two fields, one
>>>>> possibility is to describe it with a `descr` attribute like:
>>>>>
>>>>> Attribute: descr {2}
>>>>> Type: struct {
>>>>> "fieldname" +0 10-byte null-terminated ASCII
>>>>> string
>>>>> "unit" +10 10-byte null-terminated ASCII
>>>>> string
>>>>> "expl" +20 60-byte null-terminated ASCII
>>>>> string
>>>>> "scale" +80 native double
>>>>> } 88 bytes
>>>>> Data: {"field1", "kg", "long explanatory field 1", 1.2},
>>>>> {"field2", "km/s", "long explanatory field 2", 24.3}
>>>>>
>>>>> This is simple and quite powerful, IMO.
>>>>
>>>> _______________________________________________
>>>> Hdf-forum is for HDF software users discussion.
>>>> [email protected]
>>>> http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
>>>>
>>>
>>>
>>> --
>>> ___________________________________________________________________________
>>> Dr. Werner Benger Visualization Research
>>> Laboratory for Creative Arts and Technology (LCAT)
>>> Center for Computation & Technology at Louisiana State University (CCT/LSU)
>>> 211 Johnston Hall, Baton Rouge, Louisiana 70803
>>> Tel.: +1 225 578 4809 Fax.: +1 225 578-5362
>>>
>>>
>>> _______________________________________________
>>> Hdf-forum is for HDF software users discussion.
>>> [email protected]
>>> http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
>>
>
>
> --
> ___________________________________________________________________________
> Dr. Werner Benger Visualization Research
> Laboratory for Creative Arts and Technology (LCAT)
> Center for Computation & Technology at Louisiana State University (CCT/LSU)
> 211 Johnston Hall, Baton Rouge, Louisiana 70803
> Tel.: +1 225 578 4809 Fax.: +1 225 578-5362
>
> _______________________________________________
> Hdf-forum is for HDF software users discussion.
> [email protected]
> http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
>
>
>
--
There is no place like $HOME
Anton Kulchitsky, PhD
HPC Specialist
University of Alaska Fairbanks,
Arctic Region Supercomputing Center
West Ridge Research Building
909 Koyukuk Drive, Suite 105
PO Box 756020 Fairbanks, AK 99775-6020
Tel. (907)450-8689 Fax. (907)450-8603
E-mail: [email protected]
_______________________________________________
Hdf-forum is for HDF software users discussion.
[email protected]
http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
