Data Analysis & Simulation

In EasyFit 3.0 - back in 2006 - we introduced StatAssist, the built-in distribution viewer tool that closely integrates with the distribution fitting features of EasyFit. Since then, StatAssist has proven to be quite a useful feature, so we decided to include it into EasyFitXL, our distribution fitting add-in for Excel.

StatAssist displays graphs and other useful properties of all the probability distributions available in EasyFit. Even though it has initially been designed as an essential part of EasyFit, StatAssist can be used as a separate application – for example, to take a quick look at a distribution curve, or to calculate the distribution statistics… read the full article

Excel has become the de facto standard application for data analysis and presentation across a variety of industries, so if you deal with random data of any kind, chances are your data is stored in Excel workbooks. However, analyzing probability data in Excel can be tricky as the standard Excel package includes no facilities for fitting probability distributions to data. That is when EasyFitXL, the distribution fitting add-in for Excel, comes in handy… read the full article

It’s been a while since we updated our blog - that’s because we have been working on a new version of EasyFit planned to be released later in October 2008. Below is a quick summary of new features in EasyFit.

(Note: The price for the new version is likely to increase, but since all licenses come with one year of free updates, you can still order EasyFit at the current price this month and upgrade to the upcoming new version for free.)

New Probability Distributions

EasyFit will include 15 new distributions:

The Burr (Singh-Maddala), Dagum (Inverse Burr), Pareto Type II (Lomax), and Log-Gamma distributions are mainly used in economics and actuarial science. We have had numerous requests for these models from some of our customers - actuaries and finance industry professionals.

The Generalized Gamma distribution is an advanced 4-parameter model including the Gamma, Weibull, and Half-Normal distributions as special cases.

The Pearson Type V (Inverse Gamma) and Pearson Type VI (Beta Prime) distributions are a part of the Pearson family of distributions often used in financial applications.

The Levy distribution is one of the few distributions that are stable and that have probability density functions that are analytically expressible, the others being the Normal distribution and the Cauchy distribution.

The Log-Pearson III (often referred to as “LP3″) distribution is the standard model recommended by the U.S. Water Resources Council for use by all U.S. Government agencies for flood frequency analysis.

The Nakagami (Nakagami-m) and Rice (Nakagami-n) distributions are used in communications theory to model signal fading under specific conditions.

The Kumaraswamy distribution is used in electrical, civil, mechanical, and financial engineering applications dealing with variables that are lower and upper bounded.

Some other new models include the Hyperbolic Secant, Error (Exponential Power), and Reciprocal distributions.

New Excel Functions

In EasyFit 4.0, we added the ability to analyze probability data in Excel, which has proven to be quite a useful feature. EasyFit 5.0 (Professional Edition) extends this functionality by introducing several new functions making it even easier to use distributions in your worksheet models.

The DistFit function allows to fit a specified distribution to your data and display the resulting model right in a worksheet. This function can be useful if you already know the underlying distribution (e.g. the Normal model) and only need to estimate the distribution parameters. The return value of this function can be supplied to several other new functions such as DistPdf, DistCdf, DistRand etc. For example, specifying

=DistCdf(DistFit(”Normal”; B1:B100); 2)

in a worksheet will fit the Normal distribution to the data in cells B1:B100, and then evaluate the CDF of the resulting Normal distribution at x=2.

A new article about generating random numbers in Excel is now available in the Tutorials section. The article describes how the standard Excel worksheet functions and the inverse transform method can used to generate random numbers from various distributions, discusses the drawbacks of this approach, and explains how the EasyFitXL add-in can be used to overcome the limitations of Excel.

The new version of EasyFit introduces a number of features targeted at business users dealing with probability data analysis, modeling, and simulation. For a complete list of new features and fixes in EasyFit 4.0, please click here.

The free 30-day trial version of EasyFit is available for download.

EasyFitXL - EasyFit for Excel

Many businesses use Excel for their data analysis & modeling needs, and even though Excel provides only a basic set of statistical functions, it can be easily extended by installing third party add-ins. An add-in is a piece of software that integrates into Excel and allows you to perform specific tasks which are impossible (or hard, time consuming etc.) to do using Excel alone.

EasyFitXL is a new Excel add-in which ships with EasyFit and allows to use most of the features available in EasyFit right in Excel. With EasyFitXL, you can fit distributions to worksheet data, view distribution graphs, perform probability calculations, and generate random numbers without the need to run EasyFit (the stand-alone application).

The installation process of EasyFitXL is very straightforward: if you have Excel (version 2000 or later) installed on your computer, the EasyFit setup application will automatically install and configure EasyFitXL to properly work with your copy of Excel.

Once EasyFitXL is installed, it can be accessed from the main menu of Excel:

In Excel 2007, it can be found on the Add-Ins page:

Along with the main menu commands, EasyFitXL provides a large number of functions which you can use in Excel worksheets and VBA applications to create advanced models dealing with uncertainty. The worksheet functions are divided into three large categories displayed in the Function Wizard:

The following worksheet and VBA functions are available for more than 40 probability distributions:

• PDF (probability density function)
• CDF (cumulative distribution function)
• inverse CDF (quantile function)
• hazard function (failure rate in reliability analysis)
• distribution mean/variance/standard deviation
• random number generation

These functions can be applied to solve a wide array of problems, ranging from simple probability calculations to Monte Carlo simulation.