________________________________
Michael Michaud wrote:

Hi Jukka,
Thank you for your answer, I was almost sure that Beanshell Attribute 
Calculator can handle it with some awkward syntax. Do we already have 
documentation about Attribute Calculator or could you create for example an 
empty page into wiki as a bookmark?
> I added some information in the wiki :
> http://ojwiki.soldin.de/index.php?title=Beanshell_Attribute_Calculator<http://ojwiki.soldin.de/index.php?title=Beanshell_Attribute_Calculator>
>It's difficult to imagine every area where a calculated attribute may help, 
>but let's improve the example part as > it comes

The road example is like reverse engineering the resultu of dynamic 
segmentation which has materialized by splitting the segments physically and 
thus is might be of some general interest. OpenStreetMap road data fits also 
this definition. By dropping unnecessary tags the number of linestrings could 
be decreased by intelligent merging.
> I see. A solution would be to replace current options "Use an attribute", 
> "Attribute" by a list of actual attributes with a checkbox for each one.
> In this case, maybe we should split the tool again to have
> - union/merge (a selection or a layer), keeping only the merge option (+ 
> option to split non adjacent linestrings ?)
> - dissolve/merge (a layer) : same options + list of all attributes (with 
> checkboxes) + aggregate unused attributes

How about having two options for the unused attibutes: Aggregate unused 
attributes/Discard unused attributes. The latter would remove the unused 
columns from the schema of the new union layer. What I have in my mind is to 
cut down file size by cutting down the number of features and by removing 
unnecessary attributes. Of course the latter is quite easy to do from "Edit 
Schema".

-Jukka Rahkonen-

Michaël

-Jukka-
________________________________
Michael Michaud wrote:

Hi Jukka,

As you guessed, I generally solve this kind of problem with a calculated 
attribute.
There are a few things to know for that.
For numeric attributes, you can do as you suggested : 100*A + B
For string attributes, use + to concatenate attributes and don't omit to add a 
separator : A + ";" + B
If your expression starts with "", + will concatenate fields, even numerics : 
"" + 1 + 2 -> 12
So the following expression should work in almost all cases
"" + A + ";" + B
(did not check for dates)

Accepting several attributes in the union/dissolve user interface would be 
nice, but
it needs some more work (especially if we want to be able to add/remove fields
from the dialog in order to manage any number of attributes).
Please, add a Feature Request for that.

Michaël


-Jukka-
________________________________
Landon Blake wrote:

So it sounds like adjacency will be important too? In other words...we don't 
want to merge features that aren't adjacent or topologically connected?

Landon

On Wed, Sep 10, 2014 at 1:43 PM, Landon Blake 
<sunburned.surve...@gmail.com<mailto:sunburned.surve...@gmail.com>> wrote:
Interesting use case Jukka. Let me think about how this might work as a plug-in.

Landon

On Sun, Sep 7, 2014 at 1:47 PM, Rahkonen Jukka (Tike) 
<jukka.rahko...@mmmtike.fi<mailto:jukka.rahko...@mmmtike.fi>> wrote:
Hi Landon,

My case last week was about parcel IDs and landuse codes and aim was to union 
areas so that polygons with same landuse and belonging to same owner would make 
one polygon.

For another use see attached images and source data in Jump JML format.  Data 
could present two highways with ref. IDs "100" and "200". Both highways have 
sections with speed limits "60" and "80". Aim is to merge segment of highway 
"100" with speed limit "80" together etc.

Image one: Original segmented data
Image two: Desired end result. Notice an extra: Highway "100" has speed limit 
"60" in two distinct places. I do not want them to be combined into 
multilinestring. OJ can handle this case with two subsequent operations: Merge 
selected features + Explode selected features.

-Jukka Rahkonen-






________________________________
Lähettäjä: Landon Blake 
[sunburned.surve...@gmail.com<mailto:sunburned.surve...@gmail.com>]
Lähetetty: 7. syyskuuta 2014 22:10
Vastaanottaja: OpenJump develop and use
Aihe: Re: [JPP-Devel] Union/dissolve by several attributes

Jukka:

Can you give me some more details on the actual union you are trying to 
accomplish? What do you integer attributes represent?

Thanks.

Landon


On Wed, Sep 3, 2014 at 4:21 AM, Rahkonen Jukka (Tike) 
<jukka.rahko...@mmmtike.fi<mailto:jukka.rahko...@mmmtike.fi>> wrote:
Hi,

I would like to union features by two or perhaps more attributes. I wonder if 
the current Union/Dissolve/Merge tool could be developed to support the use of 
combined classes. In my use case I have two integer attributes which define the 
classes and it is a bit tricky to calculate a new concatenated field from 
those. Perhaps it is possible to do with the Beanshell Attribute Calculator but 
it is not obvious for me how. An example: I have two integer attributes and I 
would like to concatenate their values to one field which I would like to use 
for merging later. If the attribute values are A=80 and B=20, how could I 
conbine them into "80-20" or something like that? Well, in this case I could do 
(100xA)+B=8020 but what to do if I had also strings to concatenate as A=80 and 
B=true? I can do the task fine with Spatialite but it would be a bit more 
fluent to do everything with OpenJUMP.

-Jukka Rahkonen-

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