Version 0.8 -- April 3, 2001
This was the first publicly-available version.
Version 0.9 -- July 3, 2001
This version was used by about 125 students at Rutgers in the Fall of 2001. Follow this link for the version 0.9 user guide
In version 0.8, the random number seed could be reset whenever YASAI paused to see if the user wanted to abort, leading to non-repeatable behavior for large models or slow processors.
Version 1.0 -- January 15, 2002
This version includes fixes of bugs discovered in Fall 2001, and some enhancements suggested in the journal paper referee reports.
YASAI now attempts to guess how many scenarios you need, and gives you a choice of accepting its guess or specifying a different number; this feature also involved a redesign of the main dialog box.
A triangular distribution generator has been added.
GENTABLE allows its arguments to have different shapes, so long as the total number of cells match.
In version 0.9, output statistics for variables having a different number of observations than the sample size were usually wrong.
In version 0.9, the arguments to GENNORMAL were rounded to integers.
GENTABLE now conforms with the specification and does not require all data to be in columns.
In version 0.9, worksheets with names like "Simulation Output blah", where blah was non-numeric, could crash YASAI.
Run times were reported incorrectly in version 0.9.
When error values are returned, they are now "true" Excel error objects.
Link updating now takes into account that some browsers may rename the add-in file from .XLA to .XLS.
The information in the "about" box has been expanded and updated.
GENTABLE has been rewritten and should be a little faster.
Some redundant argument type checking code has been deleted.
The tab order and tool tips in the main dialog box have been tweaked.
Version 1.1 -- April 23, 2002
This was a substantial maintenance and feature enhancement release.
Output and Parameter names are now sorted alphabetically on the output report.
YASAI Functions are now accessible from the "Statistics" category of the Excel "Insert Function" dialog box.
The YASAI version, same-seed setting, and random number seed are now included in the output report.
Users may specify a random number seed without the "same seed" box being checked.
A confirmation box now appears if user tries to simulate a sheet whose name begins "Simulation Output".
Simoutput now interprets TRUE as +1, rather than -1. It also returns a value with the same datatype as it is passed.
Added message box preventing YASAI from running without first having an open workbook (previously, selecting YASAI with no open workbook crashed Excel).
Substituted L'Ecuyer's MRG32K3A
random number generator for VBA's RND(), which is not very sophisticated. The MRG32K3A random number generator function is called YRandom(). This change should result in more robust simulation results, although simulations run significantly slower. However, there are some savings in memory, because a potentially large array that had to be maintained to work around a RND() seed-setting bug in Excel 97 has been eliminated (see "bugs fixed" for version 0.8).
Version 1.15 -- March 15, 2005
A minor maintenance release focused on the issue of link repair. Excel insists on using absolute pathnames in the "links" it uses to locate user-defined functions, which causes no end of trouble.
Link repair is now attempted both on the internal link array and on worksheet formula text. This should reduce the chance that users will have to manually repair text links. Also, if Excel asks whether you want to repair links, it now no longer matters if one answers "yes" or "no".
We have created an experimental auto-installer program to simplify installation. It takes care of deleting old versions of YASAI, and also tries to install in a fixed path that is likely to exist on most systems,"C:\Program Files\Microsoft Office\Office\Library
". This change should reduce the likelihood that files moved between different computers will need link repair. The installer may need further refinement, especially in dealing with systems where YASAI has already been installed.
Link repair should now work under Office XP (see "link repair" under "features added"). The link repair strategy version 1.1 employed in Office 97 and 2000 did not work under Office XP. Text-based link-repair is also needed.
Version 2.0 -- February 2, 2007
A major release with significant new functionality and major bug fixes.
A wide variety of charts can be created from the most recent simulation. This capability was developed several years ago, but needed more debugging.
The install.xls file should make installation easier on many systems. This file replaces the less reliable version 1.15 auto-installer. [Note: due to subsequent problems, the installer was deprecated in 2008 and is no longer recommended.]
We have added a generator for geometric random variables.
Greatly improved handling of situations in which two or more outputs have the same name. Outputs with the same name are now correctly "pooled" into a single set of observations, whose observation count may exceed the originally specified sample size. This change involved restructuring some of the internal data arrays. Previously, having two outputs with the same name could crash YASAI.
Although it has been hard for us to test, we have made changes to make YASAI function better with non-English language versions of Excel. Specifically, YASAI will attempt to insert its menu options into the foreign-language equivalent of the "Tools" menu, for example "Outils" in French Excel.
We have corrected a bug that could result in inaccurate data on the "Simulation Output" sheets.
Version 2.1 -- February 24, 2010
A maintenance release with bug fixes and improved Excel 2007 compatibility.
Previously, SIMOUTPUTs with large means but zero or infinitesimal variance could cause YASAI to crash. This bug has been corrected, and YASAI simply reports a zero standard deviation.
In earlier versions, attempting to produce a chart in which all data series are deterministic and identical could cause a crash. This bug has been corrected, although the resulting charts are of course not very interesting.
Version 2.1 corrects two different bugs affecting models with more than 10 SIMOUTPUTs. Previously, models with 11 SIMOUTPUTs would run, but produce blank simulation reports. Models with 12 or more SIMOUTPUTs would crash YASAI. Both of these bugs have been corrected.
In Excel 2007, charts containing only a single histogram used to contain a malformed legend. This bug has been corrected, and a standard legend should appear. The bug did not affect Excel 2003 users.
In Excel 2007, the appearance of the Add-Ins ribbon has been altered. "YASAI Charts..." no longer appears twice. Instead, there is a single "YASAI" menu button which pops up two choices, "Simulation" and "Charts". The Excel 2007 Add-ins ribbon buttons are now created in a different manner from the Excel 2003 menu choices, and it is hoped the new procedure will be more robust.
Version 2.2 -- September 20, 2010
A minor maintenance release, fixing a bug introduced in version 2.1. Version 2.1 would crash if run on a sheet with no SIMOUTPUTs. This behavior has been corrected. As in Version 2.1, sheets with more than 10 outputs should work properly.
Version 2.3 -- July 26, 2011
Another minor maintenance release, improving compatibility with Excel 2010. Link repair for a downloaded YASAI spreadsheet would sometimes crash VBA under Excel 2010; this behavior has been fixed.
Version 2.4b -- November 21, 2013
Preliminary version with Mac Excel 2011 compatibility.
Version 2.4 -- December 2, 2013
Version compatible with Mac Excel 2011 (while still maintaining full Windows Excel compatibility). The only functionality that does not work on the Mac platform is histogram charting (cumulative charting works). Histogram charting is disabled on the Mac due to an apparent Excel bug. This version also contains minor bug fixes.
March 28, 2014
with Excel 2013.
When using earlier versions
of YASAI with Excel 2013, the
add-ins tab would
often disappear from
the ribbon, and Excel
would have to be
closed and restarted
to make it reappear.
This behavior, due to
changes in the
semantics of the
ribbon interface, has
May 18, 2016
Compatible with Mac Excel 2016,
although simulation performance is poor compared to other
versions of Excel. Introduces the new SIMPARAMETER
function which should replace PARAMETER and makes it much
more straightforward to test all possible combinations from
different parameter lists. Also introduces a lognormal
distribution generator and various bug fixes.
This, version, like version 2.5, is
compatible with Windows Excel 2016, as well as all previous
Windows versions of Excel.
June 25, 2017
This version has the ability to simulate models with more than
one worksheet, through a new "simulate all sheets" option in the simulation dialog box.
The vertical axis of histogram plots is now a probability scale, and there were some bug fixes.
October 8, 2017
This minor releases fixes an incorrect
expression datatype in the workbook activate event handler.
It seemed to work fine on nearly all computers, but would
occasionally throw errors.
2.7.2 -- January 17, 2018
This minor releases fixes several
Models with more than 11
simparameters did not work properly. This problem
is now fixed. Thanks to Teddy Boyce for pointing
out the bug, diagnosing the error in the code, and
providing some of the code to fix the problem.
Charts in which there was just
one bucket or tick mark below 0 would have all their
negative datapoints dropped or invisible. Thanks
to Tito Homem-de-Melo for finding this problem, which
turned out to be due to counterintuitive and
undocumented behavior in Excel's FLOOR function.
It is now fixed.
We have recently been observing very
slow simulation performance in Mac Excel 2011. We do
not know the reason for this performance problem and it
seems to affect all recent YASAI versions. If anybody
has a fix, please contact Prof. Eckstein.
June 6, 2019
A major release with several
significant new features, some minor enhancements, and some
bug fixes. The lion's share of the work was performed
by Sohum Sanghvi, a Rutgers independent study student, over
the Spring 2019 academic semester. The new features
There is now a "dump internal
data" option in the simulation dialog box.
Checking this option causes full sample data for all
outputs to be dumped to a new worksheet ply at the end
of each simulation.
YASAI has functions to
automatically the scenario with the highest mean value
of a given variable in a simulation output report, or
the lowest mean value. This functionality was
contributed by a user, Teddy Boyce.
Hypothesis testing: YASAI
can now perform t-tests to evaluate the
statistical significance of the difference between the
sample means displayed in the output.
The bug fixes and minor enhancements
are as follows:
Histogram charts have been
re-enabled when using Mac Excel 2016 (but not Mac Excel
2011, where they are not properly supported).
Histogram and cumulative charts
can be mixed in any order without corrupting the axis
Internal time values are now
represented differently. This change is intended
to prevent crashes on Macs configured for some countries
outside the USA.
The code that adds and removes
the YASAI functions from the menu bars and ribbons has
been partially reworked. When viewing a chart,
applicable YASAI functions (creating more charts or
hypothesis testing, but not simulation or scenario
highlighting) are immediately available without having
to switch back to viewing a worksheet.