[Qgis-developer] Reading a new type of file natively in QGIS

Alex Mandel tech_dev at wildintellect.com
Fri Dec 12 16:23:25 PST 2014

Yes, that's not foreign to me.

I think for QGIS you would likely want to undo the matrix in to long
format rows.
Dest, Orig, Value

With data in that format in a db it would work fine to query out and
display the data in various ways. Also Dest and Origin could then be
joined to Points and you could do things like give me all end points
from Dest A where dist or time is less than x miles or 1 hour.

I could chat with my colleagues who do more transportation analysis to
see what they think.

Without understanding how you want to actually use the data it's hard to
know where to start. But the format you have is familiar to many of us
as a Distance Matrix (though the value can be anything).

Perhaps a plugin to transform it on the fly using Numpy?


On 12/12/2014 04:14 PM, Pedro Camargo wrote:
> Hi Alex,
>                  This matrix is a transportation demand matrix, where the
> indices represent the node of origin and the node of destination in the
> network. They could be interpreted as vectors, I think, if you think in the
> sense that both the origin and the destination do have coordinates, but
> representing them as lines do not make any physical sense.
>    Did my explanation help at all?
> THanks,
> Pedro
> On Fri, Dec 12, 2014 at 2:46 PM, Alex Mandel <tech_dev at wildintellect.com>
> wrote:
>> On 12/11/2014 08:21 PM, Pedro Camargo wrote:
>>> Hi group,
>>>                 During my discussions with people from the transportation
>>> modeling world, some people pointed out a few features that would be nice
>>> to have in order to use QGIS more intensively by our group.
>>>                 The most important issue, however, was the possibility of
>>> open matrices in a very efficient way (reading matrices that are
>>> 10.000x10.000 in dbf format means reading 10e8 lines, which takes a VERY
>>> long time and defeats the purpose of using QGIS for some things.
>>>                 A very good alternative would be using an open source
>>> format from the project "open model data"  (
>>> https://sites.google.com/site/openmodeldata/) which is based on HDF5.
>>>                 I see that QGIS can already open raster data in HDF5
>>> format, but in this case, the data would be a matrix with indices and
>> all.
>>>                I regret to say that my programming skills, specially in
>>> C/C++ are not nearly good enough to evaluate the effort that it would
>> take
>>> include such support and have, inside QGIS, a possibility of viewing such
>>> matrices, which would allow people from the transportation world (and I
>> am
>>> the first volunteer) to develop the necessary plugins to manipulate the
>>> matrices and generate the commonly used statistics.
>>>               Can anybody tell me what type of effort it would take and
>> if
>>> it is at all of interest of the QGIS community?
>>> Thanks a lot,
>>> Pedro
>> This is more a question for GDAL/OGR I think.
>> How do your matrix values relate to map objects? Is your matrix a vector
>> or a raster?
>> What do you want to do with the data inside QGIS?
>> Thanks,
>> Alex
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