Many of the Gwyddion data processing modules produce graph as an output. Graphs can be exported into text files or further analyzed within Gwyddion by several graph processing modules. These modules can be found in the Graph menu in the Gwyddion main window. Note that the number of graph modules is quite limited now and consists of basic modules for doing things that are very frequent within SPM data analysis. For more analytical tools you can use your favorite graph processing program.
In this section the graph modules present in Gwyddion are briefly presented.
First of all zooming and data reading functions are available directly in the graph window:
Graph level is a very simple module that currently performs linear fit of each graph curve and subtracts the fitted linear functions from them.
The curve fitting is designed namely for fitting of statistical functions used in roughness parameters evaluation. Therefore most of the available functions are currently various statistical functions of surfaces with Gaussian or exponential autocorrelation functions. Nevertheless it also offers a handful of common general-purpose functions.
Within the fitting module you can select the area that should be fitted (with mouse or numerically), try some initial parameters, or let the module to guess them, and then fit the data using Marquardt-Levenberg algorithm.
As the result you obtain the fitted curve and the set of its parameters. The fit report can be saved into a file usingbutton. Pressing button adds the fitted curve to the graph, if this is not desirable, quit the dialog with .
The module for fitting of force-distance curves is very similar to the general curve fitting module, it is just specialized for force-distance curves. Currently, the module serves for fitting jump-in part of force-distance curve (representing attractive forces) using different models:
Note that the curve being fitted must be a real force-distance curve, not a displacement-distance or sensor-distance curve. Recalculation of cantilever deflection into force should be done before calling this module.
Also note that for small cantilever spring constants the amount of usable data in attractive region is limited by effect of jumping into contact.
Critical dimension module can be used to fit some “typical” objects that are often found while analyzing profiles extracted from microchips and related surfaces. These objects are located in the graph and their properties are evaluated.
The user interface of this module is practically the same as of the graph fit module.