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<p>Hi,<br>
</p>
The Expressions Plus plugin is there for sharing expressions that
are of broader interest but for whatever reason did not make it
(yet) to core [1]<br>
<br>
Would be great to push there whatever is interesting so we don't
have to install a bazillion different plugins.<br>
<br>
Matthias<br>
<br>
[1] <a class="moz-txt-link-freetext" href="https://plugins.qgis.org/plugins/qgsexpressionsplus/">https://plugins.qgis.org/plugins/qgsexpressionsplus/</a><br>
<br>
<div class="moz-cite-prefix">On 19/10/16 21:42, DelazJ wrote:<br>
</div>
<blockquote
cite="mid:CAECJsSo9dd3++=jH5yUP3Rv-SJ7UpnOmCM6y+KysqAE0k7aBtQ@mail.gmail.com"
type="cite">
<div dir="ltr">
<div style="font-family:'Calibri','sans-serif'">
<div dir="ltr">
<div dir="ltr"><font size="2">Hi all,</font></div>
<div dir="ltr"><font size="2">Thank you all for your
answers. This is really a great community! I already
knew that but let me say it loudly. It also shows all
the capabilities of QGIS to solve a problem.</font></div>
<div dir="ltr"><font size="2"><br>
</font></div>
<div dir="ltr"><font size="2">Nicolas, as Andreas said, I'm
looking for something dynamic, live. </font></div>
<div dir="ltr"><font size="2"><br>
</font></div>
<div dir="ltr"><font size="2">The virtual layer can indeed
be an option despite the creation of an intermediate but
somehow live layer. Would be nice to have Andreas
questions documented in the user manual so that users
are fully aware of any potential limitations of the
feature or its great power.</font></div>
<div dir="ltr"><font size="2"><br>
</font></div>
<div dir="ltr"><font size="2">Another powerful feature I
often neglect is the function editor. Maybe because
there are so many functions in the list that I end up
thinking that their combination would be enough. I think
it's the way I will go as no intermediate layer is
involved and despite your remarks (which are not far
from Andreas questions about virtual layers). Thank you
Germán for reminding me. </font></div>
<div dir="ltr"><font size="2">That makes me wonder: we have
in QGIS, ways to share processing scripts and models, to
share symbols, styles... What about something to share
custom expression functions? Plugins somehow already do
that but I think there are many people that have an
operational code (that fills some small and common needs
like mine) but don't have time/skills to create the Gui
around. Does it sound reasonable/feasible? Maybe should
I open a discussion in dev list (or a ticket)?</font></div>
<div dir="ltr"><font size="2"><br>
</font></div>
<div dir="ltr"><font size="2">Back to the approach I was
following to solve the issue (combining default
functions in expression) may I understand that it was
endless? No way to group by when using aggregate
function...?</font></div>
<div dir="ltr"><font size="2"><br>
</font></div>
<div><font size="2">Greetings,<br>
</font></div>
<div><font size="2">Harrissou<br>
<br>
</font></div>
<div dir="ltr">
<div dir="ltr"><font size="2">Envoyé depuis mon HTC</font></div>
</div>
<font size="2">
</font></div>
<br>
<div id="m_1040782985649138824htc_header">----- Reply message
-----<br>
De : "Germán Carrillo" <<a moz-do-not-send="true"
href="mailto:carrillo.german@gmail.com" target="_blank">carrillo.german@gmail.com</a>><br>
Pour : "Neumann, Andreas" <<a moz-do-not-send="true"
href="mailto:a.neumann@carto.net" target="_blank">a.neumann@carto.net</a>>,
"Harrissou 'DelazJ'" <<a moz-do-not-send="true"
href="mailto:delazj@gmail.com" target="_blank">delazj@gmail.com</a>><br>
Cc : "Nathan Woodrow" <<a moz-do-not-send="true"
href="mailto:madmanwoo@gmail.com" target="_blank">madmanwoo@gmail.com</a>>,
"qgis-user" <<a moz-do-not-send="true"
href="mailto:qgis-user@lists.osgeo.org" target="_blank">qgis-user@lists.osgeo.org</a>>,
"Nicolas Cadieux" <<a moz-do-not-send="true"
href="mailto:nicolas.cadieux@archeotec.ca" target="_blank">nicolas.cadieux@archeotec.ca</a>><br>
Objet : [Qgis-user] Using aggregates functions to count
intersected features from another layer<br>
Date : mer., oct. 19, 2016 18:04</div>
</div>
<br>
<div dir="ltr">Hi All,
<div><br>
</div>
<div><br>
</div>
<div>Harrissou, have a look at [1] for a very similar question
and one possible solution using the Function Editor (of
course, instead of sum you would use count).</div>
<div><br>
</div>
<div>Do you other devs find that approach useful? Any hint for
keeping the index up-to-date?</div>
<div><br>
</div>
<div>Is there any interest in having this kind of functions
available for QGIS expressions? I could help with that.</div>
<div><br>
</div>
<div><br>
</div>
<div>Regards, </div>
<div><br>
</div>
<div>Germán</div>
<div>--</div>
<div>[1] <a moz-do-not-send="true"
href="http://gis.stackexchange.com/a/212762/4972"
target="_blank">http://gis.stackexchange.com/<wbr>a/212762/4972</a><br>
</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2016-10-19 7:42 GMT-05:00 Neumann,
Andreas <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:a.neumann@carto.net" target="_blank">a.neumann@carto.net</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div
style="font-size:10pt;font-family:Verdana,Geneva,sans-serif">
<p>Good idea to use a virtual layer for that! It is
probably also more efficient than a QGIS expression.</p>
<p>Just to understand the virtual layers correctly:</p>
<p>when is the query behind the virtual layer executed?</p>
<p>- at every redraw?</p>
<p>- once at creation?</p>
<p>- at project reload?</p>
<p>Aren't the virtual layers automatically updated, at
least when the project reloads?</p>
<p>Are the results cached or not?</p>
<p>Would also make sense to add a "update" option for a
virtual layer, if that doesn't exist yet.</p>
<p>Greetings,</p>
<p>Andreas</p>
<div>
<div class="m_1040782985649138824h5">
<p> </p>
<p>On 2016-10-19 14:32, Nathan Woodrow wrote:</p>
<blockquote type="cite" style="padding:0
0.4em;border-left:#1010ff 2px solid;margin:0">
<div dir="ltr">Maybe using a virtual layer query
via DB Manager will work. You have full SQL
join support. Speed isn't always the best but
gives you the full power of SQL which is the
correct way to do this IMO.
<div> </div>
<div>E.g SELECT LayerA.id, COUNT(*) FROM layerA </div>
<div>JOIN layerB ON ST_WithIn(layerA.geometry,
layerB.geometry)</div>
<div>GROUP BY layerA.type</div>
<div> </div>
<div>Although you can't do an update but you can
make a new layer with the new counts.<br>
<div> </div>
<div>- Nathan</div>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Wed, Oct 19, 2016 at
10:22 PM, Neumann, Andreas <span><<a
moz-do-not-send="true"
href="mailto:a.neumann@carto.net"
target="_blank">a.neumann@carto.net</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex">
<div
style="font-size:10pt;font-family:Verdana,Geneva,sans-serif">
<p>Well yes - but that is not a "live"
point in polygon. It create separate
layers which need to be kept up-to-date.</p>
<p>Harrissou was after a "live" point in
polygon, which is automatically kept
up-to-date through a QGIS expression.</p>
<p>Maybe Nyall knows how to write the
correct aggregate expression for that?</p>
<p>Greetings,</p>
<p>Andreas</p>
<div>
<div
class="m_1040782985649138824m_-566526819833031328h5">
<p>On 2016-10-19 14:11, Nicolas
Cadieux wrote:</p>
</div>
</div>
<blockquote style="padding:0
0.4em;border-left:#1010ff 2px
solid;margin:0">
<div>
<div
class="m_1040782985649138824m_-566526819833031328h5">
<div> </div>
<div>Try this.</div>
<div> </div>
<div><a moz-do-not-send="true"
href="http://www.qgistutorials.com/fr/docs/points_in_polygon.html"
target="_blank">http://www.qgistutorials.com/f<wbr>r/docs/points_in_polygon.html</a></div>
<div> </div>
<div>Nicolas</div>
<div><br>
Le 19 oct. 2016 à 06:37, DelazJ
[via <a moz-do-not-send="true"
href="http://OSGeo.org"
target="_blank">OSGeo.org</a>]
<<a moz-do-not-send="true">[hidden
email]</a>> a écrit :<br>
<br>
</div>
<blockquote style="border-left:2px
solid #cccccc;padding:0 1em">
<div>
<div dir="ltr">
<div>
<div>
<div>
<div>
<div>
<div>Hi,<br>
<br>
</div>
I have a polygon
layer and a point
one.</div>
I'd like to calculate
for each polygon
feature, the number of
points that it covers.
I thought the
aggregates functions
could help me find an
easier and straight
expression to perform
this (without creating
intermediate layers)
but I fail to find any
correct syntax. <br>
<br>
</div>
I tried aggregate
('mypoint', 'count',
"id", intersects
($geometry,
geometry($currentfeature)))<br>
<br>
And many variants of
the fourth option but It
always return the total
of points or an error.
Actually this option is
a filter and I wonder if
i'm not missing a "group
by" option in the
aggregate function
(which seems to be the
appropriate one in my
case). Is it possible?</div>
</div>
<div>The work around I found
is to populate an ad'hoc
field in the point layer
with overlapping polygon
id, thanks to the
SpatialJoin plugin, then I
create a one-to-many
relation in the project
between the two layers in
other to use
relation_aggregate
function.</div>
<div>But I expected
something more direct.</div>
<div><br>
Any hint, please?<br>
<br>
</div>
Thanks,</div>
Harrissou</div>
<br>
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