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<div name="messageBodySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;">Hello Martin,
<div><br /></div>
<div>yes you are right.</div>
<div><br /></div>
<div>The terminus „Node valence“ is from topology and is defined as the number of</div>
<div>outgoing and incoming lines by a node.</div>
<div>You are example is correct: </div>
<div>a) a T Intersection has val=3</div>
<div>b) a Cross val = 4</div>
<div>c) a „one-way-street“ the end/starting point has val = 1</div>
<div><br /></div>
<div><br /></div>
<div>So i need to run it of the level of database as i assume.</div>
<div><br /></div>
<div>Thanks for your reply so far.</div>
<div><br /></div>
<div>If somebody knows to do it more „user friendly“ i would be happy to learn it.</div>
<div>I have some rudimentary knowledge of running SQL but last time used 15y ago ;-)</div>
<div><br /></div>
<div>Thanks to all of you. It is a great group to be honest.</div>
<div><br /></div>
<div>Pat</div>
<div><br /></div>
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<div name="messageReplySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;"><br />
On 13. Apr. 2017, 04:44 +0200, Martin Bain <Martin.Bain@lismore.nsw.gov.au>, wrote:<br />
<blockquote type="cite" style="margin: 5px 5px; padding-left: 10px; border-left: thin solid #1abc9c;">
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Hi Pat,</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">I saw your previous question went unanswered. I’m not familiar with the term valence, I’m guessing you want the number of lines that meet at a point. If you had like a roads layer then three streets would meet at a T intersection – the node would have a valence of three, for a cross intersection the valence would be four.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">I’ll start the ball rolling by offering a possible solution, then maybe some bigger brained folks might give a better way of doing it.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">There’s probably a sequence of steps you could do to get your end result, maybe something in the processing toolbox? Being a bit of a database guy, I reached for the DB Manager and came up with the SQL below which can be loaded as a point layer. THIS QUERY ASSUMES YOUR LINES ONLY MEET AT THE ENDS, IF ONE LINE INTERSECTS ANOTHER IN THE MIDDLE IT WONT BE COUNTED.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">The inner select statement returns a set of points. It is a UNION query of two parts, the first part selects each line’s start point and its X and Y coordinates and the second part does the same for the end point of each line.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">The outer select statement groups the matching points together and gives a count. The last line in the query “HAVING VALENCE>2” filters out any results with a valence less than three, you can adjust the number for your needs or leave it out altogether and filter the rows in QGIS.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Cheers,</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Martin.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">SELECT GEOMX,GEOMY, GEOM, COUNT(*) AS VALENCE</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">FROM</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">(</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">SELECT "LCC_WATER_PIPES"."Namecompon",</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">"LCC_WATER_PIPES"."MI_PRINX",start_point(</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">"LCC_WATER_PIPES"."geometry") AS GEOM ,</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">X(start_point("LCC_WATER_PIPES"."geometry")) AS GEOMX,</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Y(start_point("LCC_WATER_PIPES"."geometry")) AS GEOMY</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">FROM "LCC_WATER_PIPES"</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">UNION</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">SELECT "LCC_WATER_PIPES"."Namecompon",</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">"LCC_WATER_PIPES"."MI_PRINX",end_point(</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">"LCC_WATER_PIPES"."geometry") AS GEOM ,</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">X(end_point("LCC_WATER_PIPES"."geometry")) AS GEOMX,</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">Y(end_point("LCC_WATER_PIPES"."geometry")) AS GEOMY</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">FROM "LCC_WATER_PIPES"</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">)</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">GROUP BY GEOMX, GEOMY, GEOM</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">HAVING VALENCE>2</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">select A.MI_PRINX,B.MI_PRINX ,intersectION(A.geometry,B.geometry) AS GEOM</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">from LCC_WATER_PIPES as A, LCC_WATER_PIPES as B</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">WHERE A.MI_PRINX<>B.MI_PRINX</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US">AND intersects(A.geometry,B.geometry)=1</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;mso-fareast-language:EN-US"> </span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif" xml:lang="EN-US">From:</span></b> <span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif" xml:lang="EN-US">Qgis-user [mailto:qgis-user-bounces@lists.osgeo.org] <b>On Behalf Of</b> phi73@gmx.de<br />
<b>Sent:</b> Wednesday, 12 April 2017 11:03 PM<br />
<b>To:</b> QGIS User List <qgis-user@lists.osgeo.org><br />
<b>Subject:</b> [Qgis-user] Detecting node valences</span></p>
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<p class="MsoNormal"> </p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif">Hello to all,</span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif"> </span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif">is there a way i QGIS to run a select over a map to get</span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif">all the nodes with a specific node valence?</span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif"> </span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif">If not i would be happy about a shortchanged reply too :)</span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif"> </span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif">thanks</span></p>
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<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif">pat</span></p>
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