As the program runs in MS Excel, it is subject to some of the whims of that application. Known issues:
- Some versions of Internet Explorer attempt to rename the file as a .zip when you download. A solution, use Firefox or another browser to download the file.
- Office for Macs does not allow macros. If you are a Mac user, this program must be run on a virtual machine.
- Sometimes you may have difficulty saving the program once your analyses are complete. To resolve, simply choose the “Save Compact File” option from the VisualDF menu on your Add-ins toolbar. This happens to me on my XP machine, but not my Win 7 machine. I have no idea why.
- Program “blinks” when creating graphs. This was required due to a known issue in Excel 2007, though it appears to be resolved in Excel 2010.
- Excel in Win 7 appears to “redraw” the graphs each time the tab is selected, taking a moment. This does not happen on my XP machine. Again, I have no idea why.
Version 2.0.4 fixes a bug with D-Max values with 3PL data.
Version 2.0.2 and 2.0.3 fixes minor bug in two-stage linking parameter importing and theta scoring.
Version 2.0 introduces full support for 1, 2, and 3PL models. This version also allows for importing multiple item parameters files, as would be the case for multi-stage linking. Update also fixes a bug that limited the number of respondents.
Versoin 1.3 fixes an error in the sorting algorithm that caused computational and charting errors when N>1000 or when number of items > 16.
Version 1.2.1 fixes a critical error in the formula for the pooled standard deviation of the ETSSD index. The erratum is here. Note that previous version correctly computed ESSD (despite the erratum) but not ETSSD.
Version 1.2 contains 4 updates: 1. Adds normed indices not presented in Meade (2010). 2. Defaults to drawing figures without individual respondent indicators. 3. Seeks out and replaces non-numeric data characters with missing values. 4. Allows graphs to be easily converted to black and white.
Version 1.1 prevents errors in the rare instances when theta cannot be computed via EAP. It also provides the potential range of the scale level indices.
Version 1.0 is the initial release of VisualDF.
Please report bugs and issues to firstname.lastname@example.org.
VisualDF was built using Visual Basic for Applications which runs in all Office applications. To view the source code, simply hit Alt-F11 when VisualDF is open. This program is offered as open source but is copyrighted using GNU GENERAL PUBLIC LICENSE. Thus, any application that borrows code from this one must also be offered as open-source. Microsoft also has obvious copyrights on the Excel program.