Selecting a subgroup excluding edges going external to the group

Feb 21, 2012 at 7:23 AM

I'm trying to select a subgroup but only want to include edges internal to that group. Is there a way where I can exclude any edges outside the subgroup? I initially tried to filter, then tried making a group, but can't seem to exclude external vertices unless I go through and manually set them to skip.

Feb 21, 2012 at 7:13 PM

You can do that if you use NodeXL's "group-in-a-box" feature, which is where each group gets placed in its own box within the graph pane.  Try this:

    1. Select NodeXL, Graph, Layout, Layout Options.

    2. In the Layout Options dialog box, select "Lay out each of the graph's groups in its own box and sort the boxes by group size."

    3. Set "Intergroup edges" to Hide.

    4. If you don't want box outlines to show, set "Width of the box outlines" to 0.

    5. Click OK.

    6. Refresh the graph.

   7. In the Groups worksheet, select a group.

If you don't want to use "group in a box," then I don't know how to select a group without also selecting intergroup edges.

-- Tony

Feb 22, 2012 at 3:24 AM

Thanks Tony ... gets me part way there, but I'm not sure what it does with the metrics. They looked a bit messed up . From my uderstanding if we 'skip' they should not be in the metrics, but if we 'hide' they still are?

It is a useful thing to be able to just select a group of relationships by attribute without including the links to notes outside the chosen filter. I do it all the time in Netdraw...its just a tick box.....to be fair there are also some things that work better in NodeXL...

Feb 22, 2012 at 2:33 PM

Correct.  If you set the Visibility of a vertex to Skip, the vertex and its incident edges are no longer part of the graph and are not counted in graph metrics.  If you set the Visibility of a vertex to Hide, the vertex and its incident edges are invisible in the graph pane, but they are still part of the graph and are counted in graph metrics.

As an aside, if you have created groups, then NodeXL gives you the option to calculate metrics for each group as if the vertices and edges outside the group don't exist.  Go to NodeXL, Analysis, Graph Metrics and check "Group metrics" in the Graph Metrics dialog box.  The group metrics appear in the Groups worksheet.

-- Tony

Feb 23, 2012 at 5:22 AM

 

ok tks for this Tony. I ran the group metrics but things don't seem to add up. For example say I know I have 19 vertices belonging to the 'Engineering' department, yet the group metrics seem to only identify 15 of them? Can't see anything special about the ones it has missed. They all have 'show' in the visibility column. I also can't make sense of the 'degree' metric. I thought it would always have to be the addition of the in-degree and out-degrees, but is seems a bigger number.

 

I can send the spreadsheet if you like…just need an email address.

Feb 23, 2012 at 6:59 AM

I assume that you created your groups via NodeXL, Analysis, Groups, Group by Vertex Attribute; and that in the Group by Vertex Attribute dialog box, you specified the Department column, which contains Categories. 

If so, it's possible that four of your vertices have "Engineering" misspelled.  It's case sensitive, for one thing, so "Engineering" vertices will end up in one group and "engineering" vertices will end up in another.  To see what’s going on, switch to the Group Vertices worksheet, which NodeXL uses to note which vertices are in which group. Sort the worksheet on the Group column (you can use the down-arrow button in the "Group" header cell to do this), then count how many vertices are in the "Engineering" group. 

To see how NodeXL computes Degree, In-Degree and Out-Degree, click the Details links in the Graph Metrics dialog box.  The short answer is that Degree is computed only for undirected graphs, and the other two are computed only for directed graphs. 

-- Tony

Feb 23, 2012 at 10:06 AM

ok...I think the issue is that I have some vertices that have no edges....really an artefact from the way the survey was done...and the group ignores them (as it should). Is there an easy way to identify these isolates and remove them?

Feb 23, 2012 at 3:57 PM

If you use Group by Vertex Attribute to create your groups, then the fact that a vertex is an isolate has no effect on whether the vertex gets put into a group.  All that matters is what is in the Department column.

If the problem is that some vertices have an empty Department, and you want to delete those vertices, then sort the Vertices worksheet by the Department column.  All vertices with an empty Department will then be bunched together in the worksheet and you can delete them en masse.

-- Tony

Feb 23, 2012 at 9:59 PM
My problem seems to be that for some reason the grouping command doesn't pick up some vertices. I am enclosing a couple of screen shots in this powerpoint file to illustrate

Laurence Lock Lee
llocklee@gmail.com
Ph: 0407001628



On 24/02/2012, at 3:57 AM, tcap479 wrote:

> From: tcap479
>
> If you use Group by Vertex Attribute to create your groups, then the fact that a vertex is an isolate has no effect on whether the vertex gets put into a group. All that matters is what is in the Department column.
>
> If the problem is that some vertices have an empty Department, and you want to delete those vertices, then sort the Vertices worksheet by the Department column. All vertices with an empty Department will then be bunched together in the worksheet and you can delete them en masse.
>
> -- Tony
>
> Read the full discussion online.
>
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Feb 23, 2012 at 10:33 PM

You cannot include attachments that way.  Instead, you can create a new "Issue" on NodeXL's Issue Tracker tab at http://nodexl.codeplex.com/workitem/list/basic and attach your workbook there.  A screenshot of a PowerPoint slide probably isn't going to be very useful.

-- Tony

Feb 24, 2012 at 4:54 AM

I have now seen the workbook you posted at http://nodexl.codeplex.com/workitem/22282.

The vertices that are missing from the groups are missing from the graph pane, too.  It's because those vertices are isolates--meaning they have no incident edges--and NodeXL ignores isolates by default.

Here is the quick fix:

1. Switch to the Vertices worksheet.

2. In the first data cell of the Visibility column on the Vertices worksheet, enter the formula ="Show".  This will cause Excel to populate the entire Visibility column with "Show".  (Contrary to what you said in your earlier post, the Visibility column in the workbook you posted is empty.)

3. Run NodeXL, Analysis, Groups, Group by Vertex Attribute again.  The missing vertices will be placed in their proper groups, and they will appear in the graph pane, too.

For more information about isolates, including an explanation of why NodeXL ignores them by default, look up "isolates" in the index at NodeXL, Help, Help.

-- Tony

Feb 24, 2012 at 6:13 AM

I can live without the isolates...I had already assumed that was why NodeXL was ignoring them. I was just reacting to you comment earlier....' the fact that a vertex is an isolate has no effect on whether the vertex gets put into a group.  All that matters is what is in the Department column'....which made me think that there was something else wrong...

Feb 24, 2012 at 6:56 AM

...and I was just reacting to your comment earlier, "They all have 'show' in the visibility column."  They do not; the Visibility column in your workbook is as empty as a donut hole.  That's what was wrong; not NodeXL, and not my many detailed answers to your questions.

-- Tony

Feb 24, 2012 at 7:50 AM
I appreciate your help and quick responses on these issues Tony.... I certainly don't want to appear ungrateful... I apologise for any offense ... it was not intended

Sent from my iPad

On 24/02/2012, at 6:56 PM, "tcap479" <notifications@codeplex.com> wrote:

From: tcap479

...and I was just reacting to your comment earlier, "They all have 'show' in the visibility column." They do not; the Visibility column in your workbook is as empty as a donut hole. That's what was wrong; not NodeXL, and not my many detailed answers to your questions.

-- Tony

Feb 29, 2012 at 8:35 AM
ok will do….

Dr Laurence Lock Lee
Ph: 0407001628



On 24/02/2012, at 10:33 AM, tcap479 wrote:

From: tcap479

You cannot include attachments that way. Instead, you can create a new "Issue" on NodeXL's Issue Tracker tab athttp://nodexl.codeplex.com/workitem/list/basic and attach your workbook there. A screenshot of a PowerPoint slide probably isn't going to be very useful.

-- Tony