[GRASS-dev] [GRASS GIS] #517: v.net.iso / v.net.alloc: keep original cat values or change output to field in attribute table instead of new map

[GRASS GIS]

#517: v.net.iso / v.net.alloc: keep original cat values or change output to field
in attribute table instead of new map
--------------------------+-------------------------
  Reporter:  effilc36     |      Owner:  grass-dev@…
      Type:  enhancement  |     Status:  new
  Priority:  minor        |  Milestone:  7.4.0
 Component:  Vector       |    Version:  svn-trunk
Resolution:               |   Keywords:  v.net.iso
       CPU:  All          |   Platform:  All
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Comment (by mmetz):

 Replying to [comment:10 mlennert]:
 > Replying to [comment:9 mmetz]:
 > > Replying to [comment:8 mlennert]:
 > > > Pinging this after a class where many students thought they did
 something wrong because the approach using cat values is not very
 intuitive and is not directly visible.
 > > >
 > > > I still think that giving the option to write the results as new
 columns in the attribute file of the network would be a nice feature to
 have.
 > >
 > > v.net.iso and v.net.alloc split some of the input lines: if the start
 node and the end node of a line belong to different classes, that line is
 split proportional to the cost difference and the two (or more) new lines
 will belong to different classes.
 > >
 > > Therefore it is not possible to simply add a new attribute to input
 lines.
 >
 > Now that you say it, it's obvious... ;-)
 >
 > > What could be done is to add a new flag that 1) creates unique
 categories and adds an attribute table with class id (iso zone) and
 distance, 2) copies original arc attributes to a separate layer with some
 lines sharing the original arc category.
 >
 > That sounds like a good idea.

 Done in r71193 for v.net.iso (new flag -u). The newly created attribute
 table has the fields cat (category value), ocat (original category value),
 center (category value of nearest center), isonr (iso band number), isolbl
 (iso band label). A side effect is that a line is now correctly split if
 it is assigned to two different centers.

 Done in r71194 for v.net.alloc (new flag -u). The newly created attribute
 table has the fields cat (category value), ocat (original category value),
 center (category value of nearest center).
 >
 > And any objection to applying in any case a default color table ? I know
 (think) this would be a first, but for these modules one has to already
 understand GRASS' category vs attributes logic in order to understand the
 results. Coloring them by default would make the user experience easier,
 IMHO. Or at least give this option a an additional flag ?
 >

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Ticket URL: <https://trac.osgeo.org/grass/ticket/517#comment:11>
GRASS GIS <https://grass.osgeo.org>