(Pro version only)
When All Test Setups have been selected in the channel selector in the Main Toolbar the Select & Link tab window is available in the SSI editor.
In the case of the Plate with 4 datasets example the Select & Link tab window looks as below when started after an adequate state space model has been estimated and selected for each of the four test setups:
The left-most part of the window is the Select & Link editor where you estimate the modes. The horizontal axis is a frequency axis ranging from zero to the Nyquist frequency. The vertical axis lists the test setups by their order in the Test Setup tree in the Data Organizer tree structure. Test Setup number 1 is the first tree item and so on.
As a wall-paper, the Select & Link editor displays singular values of the spectral density matrices that has been normalized with respect to the area under the largest singular value curve. If multiple test setups are present the normalized singular values calculated for each test setup have been averaged to obtain the displayed curves. The absolute scaling of the singular values is arbitrary since their peaks are only used to indicate where structural modes might be.
In the present example there are four test setups with each five transducers, and in order to obtain the presented five curves the following operations have been performed:
The 5x5 dimensional spectral density matrices of test setup 1 thru 4 have been estimated.
For all test setups all the spectral density matrices have been decomposed using the singular value decomposition. The result is 5 singular values and 5 singular vectors for each of the spectral density matrices. The singular values and the singular vectors are ordered in singular value descending order for each of the spectral density matrices, i.e. the first singular value is the largest.
For each test setup the singular values are normalized. The normalization factor corresponds to the area under the first singular value curve. This normalization prevent that week modes only appearing in one or few test setups disappear.
Finally, the first singular value curve of all test setups are averaged frequency by frequency. This operation is repeated for the second thru fifth singular value curves.
By using these averaged singular value curves all modal information can be presented in one display no matter how many transducers and test setups there are. Since this normalized and averaged curve is constructed from several transducers and several test setups the dB reference value of this display is always chosen as 1. If you want to zoom to a specific frequency range you can do this from the Zoom Bar.
The way to estimate a mode in this Select & Link tab window is illustrated below.
You can either press the Add New Modes button 
in the Stochastic Subspace Identification toolbar or you can use the context-sensitive menu and select the Add Mode menu item.
In both cases a blue vertical cursor will appear together with blue diamonds that snaps to the nearest local mode of each test setup as shown below:
To select and link all the snapped local modes, represented by the crosses selected by the diamonds, simply double-click on the left mouse button. To abort the estimation press Add New Modes button again.
When the estimation is done the vertical line link the crosses that were used to create the global mode. In the top and bottom the vertical line lock itself on the average frequency of the estimated global mode. Further, a green box will appear instead of the diamond to indicate the crosses that were used to create the mode. Below, the editor is shown after the estimation:
As seen the global mode is now drawn in green and in the Mode List below it is presented as an icon. The mode remains drawn in green as long as it is selected. You can now immediately press the Animate tab to inspect the estimated mode shape.
If you have a system as the Plate 4 Datasets example with repeated modes things are a little more complicated than if all modes are well-separated as above.
To estimate the two repeated modes around 1900 Hz in the Plate example it is recommendable to zoom to a small frequency range around the repeated modes using the Zoom Bar:
It is now clear that there are two almost repeated local modes in the test setups and it is no longer a difficult task to estimate both of them as shown below:
You can always edit the currently selected (green) mode. In this case you edit the existing local modes test setup per test setup.
This feature is very applicable in cases with close modes as is the case in the example below:
It might be that the local mode seems wrong for e.g. test setup number 4. To activate the edit mode, start by selecting the mode you want to edit. Then click the edit mode button 
on the SSI toolbar. You can also activate the edit mode from the context-sensitive menu by selecting the menu item Edit Mode as shown below:
You have then activated the edit mode which will stay active until you either press the button / menu item again or press the <Esc> key or the Animate tab in the editor.
When you press the left-hand mouse button down and keep it down you will see a green diamond drawn around the crosses of the selected global mode with a blue cursor image behind the local mode you want to edit as shown bellow:
The blue cursor image shows which local mode/test setup you are editing since the blue line is drawn from the original position of the local modes of the surrounding test setups. The blue diamond shows you the currently snapped local mode. If you release the mouse button the new local mode will be used instead of the old and the global mode is be re-estimated as shown below:
If the project has multiple data sets and you want to exclude the influence of some of these data sets on a mode you can delete the data set while the edit mode is turned on.
Point at the local mode/data set you want to exclude and select the menu item Delete Data Set from Mode from the context menu as shown below:
There will then no longer be a green box surrounding the local mode. To include the data set again simply point and click on a local mode of the test setup.
You can always delete the currently selected (green) mode either by pressing the <Del> or <Delete> keys, or from the context-sensitive menu by selecting the Delete Mode menu item as shown below:
Note: You can use the General 2D Display Options and 2D Display Properties with this display.