Wednesday, 9 August 2017

Shared matches - matches who match both my paternal and maternal lines

This is just a quick post, to show the information I looked at, in order to reply to a question Debbie Kennett asked on the ISOGG DNA-NEWBIE mailing list.  The question was "how many people have double matches in their tree, ie, where a person has a match with both your mother and your father."

Now, I don't have my father tested - he passed away in 2001.  However, I do have all four of his siblings tested, as well as a paternal first cousin of theirs.  So, whilst it's not quite the same, as I know there are still some areas of my chromosomes where none of my Dad's relatives match me, the data should give me a reasonable indication of the overlap between my matches and the two different sides of my family (which, as far as I am aware, are not related to each other).

I had actually noticed this 'matching to both sides' some time ago, when I first started playing about with my FTDNA "in common with" (ICW) data and the Pajek program (which I mentioned in my previous post) just to see what the program did.  I realised then that eleven of my matches seemed to match both sides of my family.  Yesterday, I decided to check the current situation in order to answer Debbie's question.

To do this, I used the DNAGedcom Client app to download my ICW file from FTDNA.  I then extracted all the matches who are in common between me and my six relatives (my mother, Dad's four siblings, and their paternal 1c).  I then used the Pajek program to display the information.  This first image was produced using the options "Energy: Kamada-Kawai: separate components"

The program can display the names associated with each point, but I have obviously removed those for privacy reasons.  It is quite clear that there are two main clusters, with sixteen matches spanning the two groups. I spread those sixteen out manually, to make them more obvious, but it's not very easy to see what is happening within the two groups, so next I tried the options "Energy: Fruchterman Reingold: 3D".  Again, I've straightened out the sixteen matches in the middle and this time allocated reference numbers to them, as well as to my relatives:

In this image, as well as the sixteen matches who link to both the paternal and maternal sides of my family, the clusters of matches for each of my father's relatives are more distinct.

(The same information can also be discovered by using a spreadsheet containing all six of the ICW files combined together and creating a pivot table with match names down the rows, and my relatives as the column headings, the table then showing a count of the match names.  By filtering on all those who match my mother, and gradually working through all those who match one or more of my paternal relatives, the full list of people matching both sides of my family can be obtained.

Doing this in a pivot table has the additional benefit that, once the list of people who match both sides is completed, it can be used to pick out the same people from the chromosome browser (CB) file*, so that the actual nature of the matching segments can be examined.

I've allocated matches to the maternal or paternal sides of my family on the basis of who shares the same segment as the match does to me.  However, in the cases where I share two segments with a match (M11 and M14) the segments are each shared by different sides of my family, so that it appears I connect to those matches through both the paternal and the maternal sides of my family:

It will be interesting to see if those matches turn out to be genuine!

Pajek Quick Reference sheet

Picking out the CB data for the "Both" people
There's probably several ways of doing this but, as I am sure there's other people in the same situation that I am in, having to learn it as I go along (and relearn it every time I want to do something similar!) these are the details of what I did:
Having cut and pasted the list of people identified as matching both sides into the first column of a new spreadsheet in the CB file, I pasted the following formula into an empty cell alongside the first match in the CB spreadsheet (replacing the blue text with the appropriate information):  =VLOOKUP([the cell reference of the Full name column for the first match in the CB spreadsheet],'[the name of the new spreadsheet containing the list of people matching both sides]'!A:A,1,FALSE) , where the A is the column in the new spreadsheet containing the list of names who match both sides, so make sure that list is pasted into the first column labelled A.  I then used 'Fill down' to copy the formula to all the cells in the CB column.  The result is the cells either show #N/A, if that match is not on the "Both" list, or the name of the match, if they are on the "Both" list.  I then used the filter function to show just the rows with the match name in and copied all the CB data for those matches into a new spreadsheet, which I used to create the table where I have allocated the matches to maternal and paternal sides.

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