There are eight drop-down menus on the main glmlab screen. For a quick explanation, see Figure 3.1.
Allows the user to load a data file for use in glmlab, using a graphical interface. A dialog box is issued confirming that the file has loaded correctly. The dialog box initially defaults to the glmlab data directory, but the default directory can be altered by moving the dummydta.m file to the required default folder/directory. See also Section 5.8.
Loads a previously saved glmlab model, restoring details such as the error distribution, link function, scale parameter, residual type and variables entered.
Saves a glmlab model, saving details such as the error distribution, link function, scale parameter, residual type and variables entered. A dialog box defaults to saving in the glmlog folder/directory, but this can be changed by moving the file dummylog.m to the desired directory.
Quits glmlab and loses all information. The DETAILS.m file will retain its information until glmlab is started again. This option is the same as pressing the QUIT button.
Exits MATLAB and hence glmlab. The DETAILS.m file will retain its information until glmlab is started again.
The binomial distribution requires two columns in the Response area; one for the observed counts and the other for the sample size. If only one column is given, it is assumed to be probabilities if all its elements are between 0 and 1, otherwise glmlab issues a warning.
After fitting models, this option should be selected to restore all options and reset glmlab. After selecting this option, the DETAILS.m file will be overwritten. This is the same as pressing the NEW MODEL button.
This option restores all the default settings. It can be selected if the user has become lost in setting the options elsewhere.
MATLAB often issues warnings. These warnings can be disabled or enabled in this menu. For more details, type help warning.
There are three parameters that the user can change:
The parameter values are stored in the PARVALS.mat file in the same directory as the DETAILS.m file (usually the glmlog directory).
This options toggles the inclusion of the constant term in the fitting of the model. By default, the constant term is included in the fitting.
The glmlab output usually contains the parameter estimates and their standard errors; and the deviance, degrees of freedom and changes in them both. The user can decide not to display the parameter estimates and standard errors by disabling Display Parameter Values. The user can also display more information--such as the number of iterations to convergence--by selecting the Display Fitting Information.
At the start of each fit, glmlab usually uses an initial estimate such that µ=y. In some cases, adjustments are made in case the response is zero. However, by selecting this option, glmlab will use the previous fitted values for the initial estimate in the iterations.
Produces residual plots from the current fit. This menu item is unavailable until a model has been fitted, after changes have been made to the model structure (altering the distribution, link function, or scale parameter), and after changing the type of residual that is to be calculated.
These plots are plotted when the appropriate button is pressed. The type of residual used depends on the type of residual chosen in the Residuals Type menu, and some plots are unavailable for certain distributions and residuals types. glmlab labels the plots as best as it is able. Apart from the plots listed below, glmlab also has available the facility to plot histograms using MATLAB's hist command. The six options are:
Since you're reading the on-line manual, you should know about this option!
This presents a screen of basic help concerning the items in the main area of the main glmlab window.
This presents a screen of basic help concerning the drop-down menu items.
glmlab uses the @ symbol to specify that two (or more) variables interact. This help screen gives brief instructions on how to specify interactions.
A brief explanation is provided of all variables returned into the workspace by glmlab. The variables returned are explained in Section 3.5.
This presents a screen of basic help for the Residuals window.
This begins a small introductory demonstration of glmlab. While the demonstration is running, the user is unable to fit models.
Places where glmlab can be found are listed here.
This option allows the user to email the author of glmlab. The author encourages you to email him if you are using the program to let him know what you think, or to give suggestions for improvements, or how you are using glmlab.
This option redisplays the splash screen that is displayed when glmlab is first started.
This is only for information. The date of the latest change--even if a minor one--is given here.
