0. Match a sample towards a reference curve

First see that you download a collection of tree ring data from the island of Namdo. This data file will be used for some examples.

You will find the file in the ITRDB database as swed302.rwl
Right-click on the link and select "Save target as" or "Save link as" (depending on your browser).

Be careful not to save the file as type "Text Document" as that will give the file the name swed302.rwl.txt. Instead see that it is saved as type "All files" or ".rwl files" (depends on your browser).

If the ITRDB database is not available, here is another copy of the file: swed302.rwl

Now, let us open that example collection!

Use either the command "Collections/Open collections from" or "Collections/Open menu for collections/Open Tucson .rwl collection".
Navigate to the swed302.rwl file and open it.

A collection with many members is created out of the swed302.rwl file.

You can sort the members by clicking on the column headers. E.g. click on "EndYear" to sort the collection by that. Then click on MemberID to get back to the initial sorting order.

When you open the collection, each member is "checked" in its little box to the very left. If you uncheck a member, it will not any longer be part of operations on the collection.

The "offset" tells how a member is synchronized relative to the other members. Members with offset=0 have their youngest rings being the youngest rings of the whole collection. E.g. as the collection is dated to 1995, then the member 6680NY with offset=10 has its youngest ring grown in 1985, i.e. that is the "EndYear" of that member.

If you double-click on a member it will open in a new "sample-window".

In this case we are going to analyze a member named "NMBS05A" and see how it matches towards the rest of the collection.

Scroll down the list to find the NMBS05A sample and uncheck it!

Then click on the button "Create Mean value sample". As NMBS05A is unchecked it will not be included in the mean value of the collection.

A mean value sample is now created from your swed302.rwl collection but with NMBS05A excluded from the summation.

The light green curve in the middle of the green curves show mean values of "deTrended" ring widths for each year.

The thinner dark green curves around this mean value curve show the standard deviation found when the mean value curve was calculated.

The upper red curves show normalized values with the mean value curve in the middle and standard deviation curves around it.

The red numbers along the top of the curve diagram show the number of members used to calculate the mean ring width number for that year.
Note: The option "Plotting window settings/Show number of stems behind your collection mean value curve" should be checked to make these numbers displayed.

Note:When you create a mean value sample from a collection, that sample is selected as your "reference" when there is no reference already selected.
Use the "Select as reference" button on a sample window to make that sample the current reference.

What is deTrended ring widths? As good or bad soil influences the ring width growth of a tree, it is reasonable to divide measured ringwidths of a tree with some sort of mean ring width value(s) for that tree to make it possible to compare ring widths from different trees of e.g. the same age but with quite different stem diameters.

The mean ring width values used are normally taken from a negative exponential curve calculated for a certain tree. That curve gives you high values for the time when the tree was young and grew with wide annual rings. It gives you low values for the time when the tree became older and grew with much thinner annual rings.

Before you create the mean value sample, you can select the type of detrending you want for this case.
If you look at the "radio buttons" under the "Create Mean value sample" button in one of the pictures above, you can see that NegExp was selected when we created the mean value curve above!

Now, click on the top of the window for your collection, swed302.rwl! (If you cannot see it, click the menu command WindowsList and then click the swed302.rwl line on that list.)

Then double-click on the member NMBS05A. It will open in a new window as shown above.

As the sample is already properly crossdated within the collection, it opened "at the right place" in relation to the reference curve. If that had not been the case, then you could have clicked the button "Make corr. analysis" a little bit to the left of the cursor symbol above. After such a correlation analysis, the curve will be repositioned to the best match of the analysis.

The black numbers along the bottom of the diagram corresponds to the number of stems used to calculate the mean ring widths for the reference. When the sample itself is created out of many stems, there will be another group of red numbers along the top of the diagram. That is of interest when you compare two mean value series and wonder how many stems there are for each ring width value for each of the series.

The red numbers 0.60, 0.55 etc show the correlation coefficient for this match for 20 years long blocks (segments). The length of these blocks is set with the "Blocklength" setting at the lower left corner in the picture above. The distance between these blocks is set with the "Blockdistance" setting.

At the Workbench tab you can get a more careful look at the correlation analysis.

The table is here sorted in descending TTest order. You may get it sorted in order of descending correlation coefficient value by unchecking a setting at "Settings/Options for matching and normalization/Sort by TTest" Normally this gives the same result though as TTest values depend on the overlap, a high correlation coefficient value with a reasonably short overlap may not be "top-rated" when sorted according to TTest value.