Use "Test towards (dated or undated) reference" for dating

Revised: Dec 10 2019. Lars-Åke Larsson

  • The Test Towards Reference command (button) can be used to check how well your dated collection members match towards a dated reference. This may be very suitable when you are building a new local collection and use a reference from a nearby area.

  • The Test Towards undated Reference command can be used to check how well a number of dated reference curves from different regions best match towards an unknown (undated) sample which is then selected as being the reference. If that unknown sample is anyhow dated, its dating information will be ignored. The command will search for the best matching position towards each collection member. This is useful either when you have no reference for the area from where your sample comes, or when your sample is of unknown origin, e.g. from a ship or you work with wood traded over long distances.
Note: Right-click the button to search for a match over a limited section of the time scale!

Crossdating using the button Test towards "...undated ref"

Sites with some shorter or longer reference curves are shown on the map.
Aneby is marked with a white dot.
For this type of crossdating operation, you need a collection with all your usable references.

The collection SSwedPISY_BEST.fh contains reference curves (=members) from several sites, some of them marked with red dots in the map above. Each reference curve (=member) has been created from its own collection with the button command "Create mean value sample". Then each such mean-value-sample has been saved as a .wid file. These .wid files have then been crossdated towards each other and added to the dated collection SSwedPISY_BEST.

Note:You might instead save your mean value files in normalized format, e.g. as several separate .d12 files and save your collection in .fil format. .d12 files contain standard deviations which are useful when "crossdating visually".
- On the other hand, data from several mean value .wid-files can be saved within a single .fh or .rwl file. This is very handy especially when sharing such a reference file with a colleague or when setting up for a demonstration.

For this exercise we will compare a segment of a sample from Aneby in Småland Bredesta_C.wid with the curves of the collection above.

The sample to be dated (Bredesta_C.wid) should be selected as the reference. By running the button-command "Test towards undated reference" (...undated ref.) we get information on how each member of the collection best matches towards that sample.

After clicking the "..undated ref." button, four more columns pop up:

By default, your collection is sorted alphabetically by MemberId. To make it sorted by e.g. T-value, click the TT column header once or twice to get the high T-value at top of the column.

You may want to uncheck those members giving low quality matches towards your reference. This can be done by hand (click) or through the button "Select best matching members". Then  you can run either the button-command "Test towards undated reference" again to get a new report with better overall results. Or you can create a mean value sample out of the still checked members and then match Bredesta_C.wid towards that mean value sample as shown in the following.

Here we are ready to create a mean value sample out of the three still checked members.

We then select that mean value sample as the reference and run a "Make corr. analysis" from the Bredesta_C sample. Results from this well discriminated match at 1845 has been copied from the Workbench to the top-right corner in the picture above.

Finally you might decide to date the Bredesta_C sample to 1845 (click the Workbench-"Dated to"-button now marked "Proposed year 1845") and then you want to check how all members match towards that.

"Test towards ref." run with the reference Bredesta_C dated to 1845.

So check all members of the reference collection (SSwedPISY_BEST) and run a "Test towards ref". See above! This gives you correlation values showing how all our reference members match the Bredesta_C sample at 1845. When such a test gives much too low CC-values for members supposed to come from nearby areas, then you might have reasons to question your dating results.

By first (e.g. provisionally) dating an unknown sample to a certain year, we can hereby (using Test towards reference, i.e. "Test towards DATED reference") get a table showing how well or bad several reference curves match the sample at that year!



Note: Select best matching members. When your collection contains MANY members, some of them will have a LOW correlation to the "reference-sample" at the tested point in time.
Then you want to uncheck those members which are not of interest for your comparisons. Then click the Select best matching members button to open a fixed selection "window". If you are only interested in matches setting the reference to 1845, then fill in that year and your minimum requirement for correlation coefficient, T-value and Overlap. (You may even leave one of these three last fields empty.) Then click "Uncheck now!".
If that resulted in too many unchecked members, click the "Check all" button on your form, adjust the values of the "Uncheck members..." window, and click "Uncheck now" again! Then click the "Clear report" button and then the Test towards undated reference button again to get a report with less members involved.

The TEXT report and your documentation

When you use the buttons "Test towards ref." and "...undated ref." you will also get a text report generated in the lower part of your screen. That report contains three main columns with subcolumns.
    The main columns show each member's current match towards
  • the current dating of the reference, (if there is no dating, the year of the best match for the collection is used.)
  • the best dating towards the reference and
  • the next best dating towards the reference.
There is also a fourth column group showing the differences between the best and next best matches. When these values are low it indicates that the there is no discrimination between the best and next best match, i.e. we have probably a false match.

You have to repeatedly click the "Test to..." button to get also the text report sorted! Please note that the members are sorted in the same way as was the checkbox member list when the "Test to..." button was pressed. This means that if you want the text report section sorted by decreasing T-value, then you have to first click the respective "Test to..." button, then click the TT-column header once or twice to get the column sorted by T-value. Then AGAIN click the respective "Test to..." button to get an updated sorted report.

Note: There is a checkbox to make the report area automatically cleared before some text generating commands: "More settings/Always clear the report area..."

Note: Sorting of members in the TEXT area is a feature of CDendro 9.5 and later.

With condensed report

Before we click on the button Test towards ref. we might see to first check the box "With condensed report" below that button! This will extend the report with a condensed version suitable for a dating report.

With suitable data, the condensed report might contain also an extra sorted list with frequently recurring year numbers like this

 Count MaxTMeanT Year 
     2  4.2  4.2 1839 
     2  4.4  4.2 1106 
    20 21.7  5.7 1845 
where 20 out of 72 members from Scandinavia and the Baltic region "voted" for the year 1845!

"Corr to target members" or Crossdating matrices

Simple crossdating is about matching a sample towards a reference, then towards another reference, then ... In the exercise above we have matched an unknown sample towards a group of reference curves. This makes crossdating faster. The button command "Corr to target members" matches a group of reference curves to a group of unknown samples. This makes crossdating still faster - more efficient! Results are presented in a matrix where the best matching combinations are displayed towards the top left corner of the matrix. See the section "Matching members of two collections to each other" to be found in the contents column under "More on using CDendro"!
Note: All reports are saved temporary in a .html file - Click the button "Open in NEW browser" to see the report.


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