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(This article was first published on » R, and kindly contributed to R-bloggers)

Last week I have updated the ‘qgraph‘ package to version 1.1.0, available on CRAN now. Besides some internal changes (especially the self-loops have been substantially improved) the most important change is the addition of a GUI interface, which can be called using the argument gui=TRUE. For example:

Will open a plotting window and the GUI that allows the user to set several parameters before plotting:

Graphical User Interface for qgraph

There is also a simplified version of this GUI for regular graphs (not correlation matrices).

What I particularly like about this GUI is that it took me only one day to implement. Making a GUI for qgraph has been on my to do list for a long time, but I never really got to learning how one of the packages that allow this work. When I found out about the ‘rpanel‘ package (which is build on ‘tcltk’) I was pleasantly amazed with how simple and intuitive it was to use.

In short, the way ‘rpanel’ works is by making a ‘panel’ using ‘rp.control()’ which is basically a list and also opens an empty GUI frame. We can use functions such as ‘rp.checkbox’ and ‘rp.slider’ to add elements to the GUI. Using these elements then does two things: an element of the list is changed (e.g., the element ‘xlim’), and a function is called on the list. This way, we can easily make an appropriate GUI element for each argument we need in a plotting function and make buttons that plot, save to PDF, etcetera.

To illustrate this I wrote a small function with comments that uses ‘plot.default’ to plot a scatter plot, and adds a small GUI frame allowing a user to zoom into the scatter plot. The codes can be downloaded here. A small example:

x <- rnorm(100)
y <- x + rnorm(100)
ScatterZoom(x,y)