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Combined and Multi-State Fits

Fits involving many observations, states or sources are best approached by initial fits to parts of the data before attempting to fit all of the data simultaneously. The final structure would typically be a single .pgo file making use of multiple observations files, but there are several routes to this end point. For examples of larger applications using the techniques described below see:

Multiple Observations Files

The structure to aim for is a master observations file (perhaps master.obs), which is a text file containing multiple include directives, which might look like:

include B0X0.obs
include B1X0.obs

include A0X0.pgo
include A1X0.pgo

The example has each band as a separate file, but other divisions between files are also possible, such as:

The include files can be nested as required. The individual files can be text files using any of the formats given in Line List Input File Format or .pgo files. The latter is new in version 10.1; including a .pgo file simply reads the lines that would appear in the Line List Window if the file was loaded into PGOPHER. While .pgo files can be easy to produce, text files are more flexible to work with, as there are only a limited number of tools available for manipulating the assignments in the Line List Window. Text files can be generated from the Line List Window using "More, Save To File". For straightforward applications use "Branch" or "Simple" format are simpler to work with, though note that for a multi-state fit directives to set the state (LowerState or  UpperState) will be needed.

When setting up with master files it is helpful to temporarily exclude part of the files to diagnose problems, and there are several ways to do this:

The Residuals Window will display the source file in the status bar when the mouse is positioned over the observation, and right clicking on the observation gives various options, including Edit which will direct the external program to show the selected observation. The included files will typically be edited in the Slave Editor (if set up correctly) or a second instance of PGOPHER. When fitting with these external programs running, the external programs will be directed to save the text or .pgo files before starting each fit.

Considerations for observations in separate .pgo files

If the observations are held as a line list in separate .pgo files, then some care is required editing the lines in these files, as there is no automatic synchronisation of states and constants between .pgo files. The most straightforward work-flow has the structure of all the .pgo files identical, and then following a fit using the master file or some other adjustment the resulting states and constants can then be exported to all the included .pgo files using "File, Export, All To..." and selecting all the included .pgo files. This will overwrite the selected files with everything from the current file, except the contents of the line list window.

An alternative work-flow has a smaller calculation in the included files, perhaps only the states directly involved in the band selected for that file. This is also possible, providing:

The Triplet-Triplet transitions in N2 example is set up in this way.