Current Status of the Loglet Lab for Windows Software Package

As of 10 July 1998, Loglet Lab for Windows 95 and Windows NT is up to version 1.1. A Tutorial for Loglet Lab is also available.

Using this version of Loglet Lab, a user can:

• fit one or more logistics, including declining logistics, to time series data of arbitrary length using a non-linear least-squares regression algorithm as described in section 4. For this purpose, a ``Logistic Fitting Wizard'' can suggest initial values for the parameters of each logistic as the point of departure for the fitting engine;

• plot the data with its fitted component logistic(s);

• plot the residuals as described in section 3.4;

• plot the data with the Fisher-Pry transform applied, linearizing the time-series data and its fitted logistic(s);

• determine confidence regions for each loglet parameter by using the Bootstrap method, a powerful modern Monte-Carlo statistical technique where the user data is used to determine the error associated with each fitted parameter.

• plot the ``bell'' view described in section 3.3, which shows the derivative (rate of change) of a component logistic and the discrete rate of change of the data;

• apply a logistic substitution model to multiple sets of time-series data as described in section 5.3, including the capacity to add hypothetical pulses as described in section 5.2;

• extrapolate a model into the past or future;

• annotate the graph (i.e., add a title and label the axes);

• print graphs using any supported Windows printer;

• export or import data to and from Microsoft Excel, or as plain text;

• consult online Help files; and

• peruse through a ``Data Gallery'' of ``classic'' sets of logistic time-series data.

Possible improvements for future versions of Loglet Lab include:

• adding an ``Undo'' function so users can correct their mistakes.

• designing a better graphing module to provide more informative and attractive graphs;

• alternative regression methods (robust, $\mathcal{CM}$);

• export a graph as a bitmap or as a Windows Metafile for use on the World Wide Web or in presentation applications such as or Microsoft PowerPoint;

• adding the option of constraining parameters to a range of values, as opposed to holding to a single constant value;

• more robust algorithms for providing initial values of parameters;

• interactive visual fitting of component logistic models, where a user could change parameters directly via a mouse. A prototype for this can be found at https://phe.rockefeller.edu/applets/index.html;

• improving spreadsheet functionality (e.g., formulas); and

• improving the general user interface.

We hope users will send us suggestions to improve Loglet Lab, the Tutorial, and this paper. Please send comments (and bug reports) to
loglet@phe.rockefeller.edu. We will also post information on the status of Loglet Lab on our web site: https://phe.rockefeller.edu/.