XLfit

XLfit is a Microsoft Excel-based plug-in which performs Regression, curve fitting and statistical analysis. XLfit generates 2D and 3D graphs and analyses data sets produced by any type of research. XLfit’s curve fitting engine allows linear and non-linear curve fits, smoothing, statistics, weighting and error bars.

XLfit includes over seventy linear and non-linear curve fitting models. Predefined categories include:

• Exponential/Log, Power Series, Sigmoidal, Hyperbolic, Yield Density, Linear, Polynomial, Dose Response, Pharmacology, Equilibrium, Inhibition
• Levenberg-Marquardt fitting algorithm

A range of statistical calculations can also be applied to the data from within the spreadsheet.

Example statistics include:

• F test and T test
• Area under the curve
• Confidence intervals
• Error values relating to parameter values or any point on the curve.

Available statistics models include Spearman's Rank Correlations, Student's T-Test, Mann Whitney U-Test, least squares, ANOVA, among others. It is possible to add your own models and statistics to the provided ones using a model editor.

XLfit was validated by The UK National Physical Laboratory[1] in 2004. The unit tests for this are provided in the model editor from version 5.4 onwards to allow each version to be easily validated.

XLfit was used by NASA to analyse the battery life of the Curiosity Mars Lander.[2]