How to build a synchronized collection from unsynchronized members

Last update: Febr 23 2018

In this lesson we will see how you can easily synchronize a number of collection members towards each other.

 This collection contains 10 members which are not synchronized. Currently their offsets are all set at zero! You can download this collection from unsync.rwl We will now see how to easily synchronize these members using the "Add best members to target collection" button of CDendro. First we have to find a member to start from, i.e. one member that matches well towards several other members of the unsynchronized collection!
 We start off by requesting a table showing how each member matches best to all other members. To make the matrix small for this demonstration, we only look at the best TTest values, but you may very well check several other items, e.g. correlation coefficient and overlap. Note that we order the matrix sorted by the best matching members.
 Here we can see that NMBS08A could be a good starting point when building a new synchronized collection. It has six matches against other members of the collection with TTest values at 6 or above.
 An alternative way to find a starting point member for a synchronized collection Another way to find a good starting point member, is to "ask" CDendro to look for collection members (samples) which match towards many other members of the source collection. I.e. to - for each member - calculate how many members it matches with a T-value greater than e.g. 6.0 and then sort all members by this value. Note: The threshold 6.0 above can be set with the command Settings/More settings/Show cross correlations/Sort by number of matches with T > 6.0 The table above with its "Sortkey" shows that NMBS08A matches towards six other members ("6.0 members") with a T >= 6.0
 So let us get a new empty target collection with the sample NMBS08A as the only member. It will then work as a "seed" that will attract other matching members of the source collection.
 The command "Alt-Click on NMBS08A" is the easiest way to both get a new target collection and have that member added to it. To achieve the same result, you might first create a new empty target collection, then double-click the NMBS08A in the source collection so it opens as a separate sample and then hit the button "Add to target collection". - Or you see that only NMBS08A is checked and then use the menu command Collections/Copy collection members to target collection.
Your target collection with its first member.
 We then turn to our unsynchronized (source) collection where we click the button "Add best members to target collection". We then set up the values as shown and click OK.
 CDendro will quickly find that NMLID1A gives a good match. Click OK to continue!
 NMLID1A will then be opened within a new "sample window" and compared towards the mean value of the members of the target collection, in this case just towards NMBS08A. If you accept this as a good match, you may very well click on the button "Add to target collection".
 Though here we wanted to investigate that match carefully, so we clicked the "Workbench" tab (1). From a comparison with several normalization methods, the table shows that this can be considered a very good match (2). So we order the sample to be added to the target collection at offset 6 as shown above (3 and 4). This addition can be done either by clicking "Add, close and show next candidate" or by clicking "Add and Stop". For this demonstration we will click "Add and Stop". Then we close the NMLID1A sample window.
 We now have two synchronized members in our target collection.
 We then turn back to our unsync.rwl source collection and click "Add best members to target collection". Please note that both NMBS08A and NMLID1A have been automatically unchecked, as they are already added to the target collection. When we click OK, CDendro will automatically update the mean value reference from our target collection and then start searching for the best matching new member.
 Still one more matching candidate, NMVK14, is found!
 The new candidate for addition, NMVK14, is now compared to a mean value of NMBS08A and NMLID1A, i.e. to a mean value of the target collection.
 After we have added it to the target collection, we have three synchronized members, all at different offsets, within our target collection.
 We will now see how this adding process may run automatically! See that the required TTest-value is set high enough, here at 7.0 Also see that the lowest allowed correlation coefficient for a 30 years long segment/block is set high enough, here at 0.35 Uncheck the "Stop before adding a candidate..." box and click OK! CDendro now first updates the mean value reference from the target collection.
 CDendro then found the next three best matching members of the unsynchronized collection and added them to the target collection at synchronizing offsets. An updated mean value was then calculated from the target between each addition. Note that only the remaining - non-added - members above are still checked!
 We will now match each remaining checked member of the unsynchronized collection towards a mean value of the target collection. To make CDendro look for the best match (and not the current match with current (wrong) datings) we use the "(Test towards)...undated ref." button as shown above. The yellow area above shows the main result from that button. NMVK11 is now the best matching member to add to the target collection. Please note that you can SORT the TT-column in ascending or descending order by clicking on the column header (TT). This is very useful when there are many members to be analyzed.
 To quickly add the remaining members, click "Add best member..." and uncheck "With block checking" before you click OK. After we have all the remaining members added at synchronized offsets we have all members synchronized. Running "Test towards rest of collection" will show very good correlation values (above). Note that by clicking on the headers of the CC or TT columns you can sort the collection members by increasing or decreasing Corr-coeff- or T-values!
 It is always a good habit to check how the individual members crossdate towards each other. With an error within the first member which was added to an empty collection (e.g. an erroneous reference!) you may very well end up with a "synchronized" collection giving you good values when running "Test towards rest of collection". Though that collection is anyhow wrong, which could be revealed by a matrix as above where some members would then give conspicuously low correlation values.
 The original unsynchronized collection above was provisionally dated to 8000 while the target (synchronized) collection then became dated to 8023. You may now create a mean value sample from your new collection and compare that to a known reference so you can set a proper endyear to your synchronized collection. In this case it was compared to a reference from the island of Nämdö and found to match at year 1895, see sync.rwl.