Baseline Spline Fit

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Baseline Spline

For fitting and subtracting spline type baselines to spectroscopic data. A spline is a continuous curve that passes through points ("nodes") selected by the user. This Igor procedure file provides an interface that allows the user to position the points and see the resulting baseline. Some sub-menus are added to the macro menu, including an option to subtract the baseline from the data.

Usage

You need to have your data wave plotted in the topmost graph window. Initialise from the macros menu, then use ctrl-1 (cmd-1 on the mac) to toggle between drawing mode, where you can drag the nodes, and normal mode, where you can interact with the graph in the usual way. The node dragging/inserting/deleting interface uses built in wave editing capabilities: option/alt-click to delete a node, click nearby an existing one to add a new node, etc. To prevent new nodes from being added toggle "Allow New Nodes" in the Macros>Spline Baseline menu. You can save and reload node positions. If you are sequentially fitting a group of similar spectra, using the same node positions for each introduces a modicum of reproducibility to the fitting. Select "Settings" to switch spline settings.

As of version 3.0 there is an option to use an Akima style spline. I incorporated code posted to IgorExchange by Michael Bongard to perform the Akima calculations.

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