This menu allows you to fit curves and nonlinear models to data, such as repeated measurements, where
the residuals may follow an AR1 or a power-distance correlation model. The explanatory variate specifies
the coordinates of the observations in the direction (e.g. time) along which the correlation model operates.
You can also specify a factor to define groups of observations for the model - the correlation model is then
defined only over the observations that belong to the same groups. You can specify your own models in
command mode using the NLAR1 procedure.
Type of Curve
This is used to select the type of curve to be fitted. There are five general classes of curve; each has several variations.
To help with the selection of an appropriate curve you can examine
example plots of each type.
Response Variate
Specifies the name of the variate containing the response (y) values.
Explanatory Variate
Specifies the name of the variate containing the explanatory (x) values.
Groups
For data classified into groups, different curves can be fitted to each group,
possibly constrained by restricting some of the parameters to values common
to all groups. The groups are specified using a factor. The correlation model
is then defined only over the observations that belong to the same groups.
The type of model that is fitted can be selected from the adjacent list. The
Common lines setting can be used to fit a single
curve with common parameters over all the groups. The
Parallel lines option extends the model to include a different constant
parameter for each group, giving a set of parallel curves, one for each group.
The Separate lines setting fits completely separate
curves, in which all the parameters differ between groups.
Direction of Response
For the exponential curves and Gompertz curve the direction of response can be selected. This determines whether the
asymptote is to the left or right. For details on the effect of direction on the parameters of the curves see the
exponential curves and growth
curves for the Gompertz curve.
Available Data
This lists data structures appropriate to the current input field. It lists
either variates for specifying the response or explanatory variate, or a
factor for specifying groups. The contents will change as you move from
one field to the next. Double-click on a name to copy it to the current input
field; alternatively, you can type in the name directly.
Action Buttons
| Run | Run the analysis. |
| Cancel | Close the menu without further changes. |
| Options | Opens a dialog where additional options and settings can be
specified for the analysis. |
| Defaults | Set the menu settings back to the default settings.
Clicking the right mouse on this button produces a shortcut menu where you can choose to set
the menu using the currently stored defaults or the GenStat default settings. |
| Save | Opens a dialog where you can save results from the analysis. |
| Further output | Opens a dialog for specifying further output from the analysis and
displaying residual and fitted model graphs. |
See Also