Dear Myles,

Regarding $rownumber, it was used to produce a unique number for each 
feature. I hadn't noticed it's not available in the "Record" functions 
any more, thanks Renato!
Instead, the $id function can also be used. I imagine that $rownumber is 
an internal function therefore it still works. But I'll update the 
documents in any case.

Regarding disappearing objects from the project, there can be many 
reasons. The preview is a screengrab at time of saving, so it shows what 
was in the map, not what will happen on opening.
If you open the attribute table of the layers, do you see any rows?
If not, then the layers are empty:
- Either you didn't save the layer edits. Remember that the layers are 
GIS files, and the project just a record of what is open in QGIS. Saving 
a project does NOT save the layers if they have unsaved edits.
- Or you created virtual layers or memory layers, that are saved as 
temporary files and disappear after closing QGIS.
If you see rows:
- Either the geometry is invalid or missing (sometimes happens, but 
would be strange in this case)
- Or it's something with the CRS. When strange things happen with 
geometry, it invariably has to do with coordinate systems and projection 
issues.

This is my quick diagnosis, maybe it helps.
But if you're new to QGIS I suggest doing some tutorials and reading one 
of the user guides. That will help you understand QGIS as a whole and 
avoid problems in the future. But most importantly, will help you make 
the most of QGIS for your work, because it's not just about SST...

Best regards,
Jorge

On 28/02/2017 21:16, Myles Bartoli wrote:
> Dear all,
>
> I’ve been been reading through and trying the tutorial on Github to try out space syntax on QGIS ( https://github.com/SpaceGroupUCL/qgisSpaceSyntaxToolkit/wiki/Tutorials ). But I’m unclear on a few aspects of it
>
> With the creation of the axial layer, I’m unsure of how $rownum is supposed to be input within the open field calculator. After selecting “update existing field”, are you supposed to just click on “Record”, or another subheading of that?
>
> With the creation of the unlink layer, are you supposed to do another “update existing field”, such as done with the axial layer?
>
> One further thing, I saved my project, and when reopening it, although the lines and points appeared in the preview picture, they do not appear on the on the project itself (although the layers of the are still supposedly present) – is this related to $rownum not being done correctly?
>
> Thanks

________________________________________

*Jorge Gil*

Honorary Research Associate


Space Syntax Laboratory

*The Bartlett School of Architecture * <http://www.bartlett.ucl.ac.uk/>*__*

UCL Faculty of the Built Environment


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