Hello Christian,
I would probably use the
modifyCoordinates()<http://pytables.github.com/usersguide/libref.html#tables.Table.modifyCoordinates>,
getWhereList()<http://pytables.github.com/usersguide/libref.html#tables.Table.getWhereList>,
and
readWhere()<http://pytables.github.com/usersguide/libref.html#tables.Table.readWhere>methods
of Tables. Probably the safest way to ensure stability would be
something like the following (though if you can make assumptions based on
the layout of your data, you could make this faster).
from itertools import product
ids = set(oldtable.cols.id)
years = set(oldtable.cols.year)
species = set(oldtable.cols.species)
ages = set(oldtable.cols.age)
for id, year, specie, age in product(ids, years, species, ages):
cond = "id == {} & year == {} & species == {} & age == {}".format(id,
year, specie, age)
newrows = newtable.readWhere(cond)
oldcoord = oldtable.getWhereList(cond)
assert len(oldcoord) == len(newrows)
oldtable.modifyCoordiantes(oldcoord, newrows)
As I said, there are probably faster ways but this would certainly work.
If you needed to you could always sort newrows too. I hope this helps!
Be Well
Anthony
On Sun, May 6, 2012 at 1:57 PM, PyTables Org <pytab...@googlemail.com>wrote:
> Forwarding,
> ~Josh
>
> On Apr 30, 2012, at 5:04 PM,
> pytables-users-bounces@lists.sourceforge.netwrote:
> > From: Christian Werner <freizeitbeauftrag...@googlemail.com>
> > Date: April 30, 2012 5:03:59 PM GMT+02:00
> > To: pytables-users@lists.sourceforge.net
> > Subject: How would I update specific rows from a table with rows of a
> second table?
> >
> >
> > Hi group.
> >
> > Please consider this scenario. I have produced a large h5 file holding
> the outcome of some simulations (hdf file holds some groups and about 5
> tables, but for my question this does not matter).
> > How I had to rerun my simulation but only for certain fields and thus I
> have a second h5 file with the same structure but only for certain fields
> of the original file (old age classes, see below).
> >
> > Or to be more verbose:
> >
> > Table (original)
> > id year species age data1 data2 data3 ...
> > 1 1990 spruce 75 1.2 3.2 3.3 ...
> > 1 1991 spruce 75 1.3 3.1 2.2 ...
> > ...
> > 1 1990 spruce 125 1.1 2.1 1.5 ...
> > ...
> > 1 1990 pine 145 1.1 2.1 1.5 ...
> > ...
> > 2 1990 spruce 45 1.2 3.2 3.3 ...
> > 2 1991 spruce 55 1.3 3.1 2.2 ...
> > ...
> >
> > I had to rerun my simulations for old vegetation classes. So this table
> only contains the following lines (e.g., spruce age > 80)
> >
> > Table (new)
> > id year species age data1 data2 data3 ...
> > ...
> > 1 1990 spruce 125 1.1 2.1 1.5 ...
> > ...
> > 1 1990 pine 145 1.1 2.1 1.5 ...
> >
> > So basically I need to use the rows of the new table and overwrite the
> corresponding rows of the old table to form the updated one. I do need to
> retain the original order (sort order id > year > species > age). Those
> columns combined give a unique row identifier...
> >
> > The final table would have the same size and order as the original table
> with only the rows containing data for old age classes updated with the new
> simulation results...
> >
> > Can anyone give me a hint how to achieve this?
> >
> > I guess I need to introduce a new (unique index) column first in both
> tables (e.g., combining id + year + species + age so I can match those
> rows by this identifier), right? Does anyone have some example code for me?
> >
> > Problem is, the 2 h5 files are about 7GB each.
> >
> > Cheers,
> > Christian
> >
> >
> >
>
>
>
>
>
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