<!DOCTYPE html><html><head><title></title><style type="text/css">#qt p.qt-MsoNormal{margin-top:0in;margin-right:0in;margin-left:0in;margin-bottom:0.0001pt;font-size:12pt;font-family:"Times New Roman", serif;}
#qt a:link{color:rgb(5, 99, 193);text-decoration-line:underline;text-decoration-thickness:initial;text-decoration-style:initial;text-decoration-color:initial;}
#qt a:visited{color:rgb(149, 79, 114);text-decoration-line:underline;text-decoration-thickness:initial;text-decoration-style:initial;text-decoration-color:initial;}
p.MsoNormal,p.MsoNoSpacing{margin:0}</style></head><body><div>Thank you Regina, noted!<br></div><div><br></div><div>/GP</div><div><br></div><div>On Wed, 2 Aug 2023, at 19:56, Regina Obe wrote:<br></div><blockquote type="cite" id="qt" style=""><div class="qt-WordSection1"><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;">I would say yes. If you have multiple components, then those components are not reachable from each other.</span></span></span><br></p><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;"> </span></span></span><br></p><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;">Note this is only considering an undirected graph.</span></span></span><br></p><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;"> </span></span></span><br></p><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;">If you have a directed graph, use pgr_strongComponents instead <a href="https://docs.pgrouting.org/latest/en/pgr_strongComponents.html">https://docs.pgrouting.org/latest/en/pgr_strongComponents.html</a></span></span></span><br></p><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;"> </span></span></span><br></p><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;"> </span></span></span><br></p><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;"> </span></span></span><br></p><p class="qt-MsoNormal"><span style="color:rgb(31, 73, 125);"><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;"> </span></span></span><br></p><div style="border-top-width:initial;border-right-width:initial;border-bottom-width:initial;border-top-style:none;border-right-style:none;border-bottom-style:none;border-top-color:initial;border-right-color:initial;border-bottom-color:initial;border-image-source:initial;border-image-slice:initial;border-image-width:initial;border-image-outset:initial;border-image-repeat:initial;border-left-width:1.5pt;border-left-style:solid;border-left-color:blue;padding-top:0in;padding-right:0in;padding-bottom:0in;padding-left:4pt;"><div><div style="border-right-width:initial;border-bottom-width:initial;border-left-width:initial;border-right-style:none;border-bottom-style:none;border-left-style:none;border-right-color:initial;border-bottom-color:initial;border-left-color:initial;border-image-source:initial;border-image-slice:initial;border-image-width:initial;border-image-outset:initial;border-image-repeat:initial;border-top-width:1pt;border-top-style:solid;border-top-color:rgb(225, 225, 225);padding-top:3pt;padding-right:0in;padding-bottom:0in;padding-left:0in;"><p class="qt-MsoNormal"><b><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;">From:</span></span></b><span class="font" style="font-family:Calibri, sans-serif;"><span class="size" style="font-size:11pt;"> Pgrouting-users [mailto:pgrouting-users-bounces@lists.osgeo.org] <b>On Behalf Of </b>glad.pen2421@fastmail.com<br><b>Sent:</b> Wednesday, August 2, 2023 12:40 PM<br><b>To:</b> pgrouting-users@lists.osgeo.org<br><b>Subject:</b> [pgrouting-users] Can pgr_connectedComponents be used to find isolated vertices?</span></span></p></div></div><p class="qt-MsoNormal"> <br></p><div><p class="qt-MsoNormal">Dear fellow pgRouting users,<br></p></div><div><p class="qt-MsoNormal"> <br></p></div><div><p class="qt-MsoNormal">As per the description of `pgr_connectedComponents`, it runs a breadth-first search to find sets of vertices "that are all reachable from each other".<br></p></div><div><p class="qt-MsoNormal"> <br></p></div><div><p class="qt-MsoNormal">Does that mean that if `pgr_connectedComponents` results in more than one connected component, some vertices are definitely not reachable from each other?<br></p></div><div><p class="qt-MsoNormal"> <br></p></div><div><p class="qt-MsoNormal">Can this be a way to guarantee that with more than 1 connected component it is guaranteed that algorithms like `pgr_dijkstra` will definitely fail on some pairs of vertices?<br></p></div><div><p class="qt-MsoNormal"> <br></p></div><div><p class="qt-MsoNormal">Thank you.<br></p></div><div><p class="qt-MsoNormal"> <br></p></div><div><p class="qt-MsoNormal">GP<br></p></div><div><p class="qt-MsoNormal"> <br></p></div><div><p class="qt-MsoNormal"> <br></p></div></div></div><div>_______________________________________________<br></div><div>Pgrouting-users mailing list<br></div><div><a href="mailto:Pgrouting-users@lists.osgeo.org">Pgrouting-users@lists.osgeo.org</a><br></div><div><a href="https://lists.osgeo.org/mailman/listinfo/pgrouting-users">https://lists.osgeo.org/mailman/listinfo/pgrouting-users</a><br></div><div><br></div></blockquote><div><br></div></body></html>