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## Creating a new database correlation

If you want to create a new database correlation to relate time-varying databases that you have opened, you can do so by opening the Database Correlation Window. The Database Correlation Window contains a list of trivial database correlations for the time-varying databases that you have opened. You can create a new, database correlation by clicking on the New button to the left of the list of database correlations. Clicking the New button opens a Database Correlation Properties Window (figure) that you can use to edit properties for the database correlation.

New database correlations are automatically named when you first create them but you can change the name of the database correlation to something more memorable by entering a new name into the Name text field. Once you have entered a name, you should set the correlation method that the database correlation will use to relate the time states from all of the input databases. The available choices, shown in figure, are: padded index, stretched index, time, and cycle.

Figure 13

Once you have chosen a correlation method, it is time to choose the input databases for the correlation. The input databases, or sources as they are sometimes called in VisIt, are listed in the Sources list (see figure). The Sources list only contains the databases that you have opened so far. If you do not see a database that you would like to have in the database correlation, you can either click the Cancel button to cancel creating the new database correlation or you can continue creating the database correlation and then add the other database to the correlation later after you have opened it. To add databases to the new database correlation, click on the them in the Sources list to highlight then and then click on the Right arrow button to move the highlighted databases into the database correlation's Correlated sources list. If you want to remove a database from the Correlated sources list, highlight the database in the Correlated sources list and then click the Left arrow button to move it back to the Sources list. Once you are satisfied with the new database correlation, click the Create database correlation button to create a new database correlation.

When you create a new database correlation, VisIt also creates a new time slider for the new database correlation. The database correlation's active time state is initially set to the first time state, which might not match the time state of individual plots in the vis window. Once you change time states using the Time slider, the plots in the vis window will be updated using the correct time state with respect to the correlation's active time state. As always, if you want to update the time state for only one database, you can select a different time slider using the Active time slider combo box and then change time states using the Time slider. Any time state changes made to an individual database that is also an input database for a database correlation has no effect on the database correlations that involve the changed database. Time state changes for a database correlation can only happen if you have selected the database correlation as your active time slider.

Figure 14