Setup window - TWINSPAN
|Top Previous Next|
The setup window is divided into four panels, which will be described in turn below.
Cut levels. This determines the abundance levels in the working data at which a species is divided into pseudospecies. A maximum of 9 cut levels can be defined. The default state is for 5 cut levels set at 0, 2, 5, 10 and 20. The radio box is set to % coverage as these are suitable values if the original data comprises percentage vegetation cover in quadrats. Select frequency if the original data are expressed in terms of relative frequency (maximum value 1). Select Pres/Abs if the working data are simply presence - absence (comprises 1s and 0s). To select your own cut levels select Custom and type in values in the line of text boxes arranged along the panel. The cut levels must be arranged from smallest to largest moving from left to right. The program ignores blank boxes.
Options. Three options are available. Maximum number of indicators per division defines the maximum number of indicator species that can be found per division. Maximum level of divisions defines the number of subdivisions of the groups that can be undertaken. The maximum is 9. Minimum group size per division gives the minimum number of samples (quadrats) in each group. Once a group size has reached this minimum level, no further subdivisions are undertaken.
Weighting. Each box in this panel gives the relative weighting given to each pseudospecies cut level. The default is all 1s, indicating that all pseudospecies are given equal weighting. If you wish to adjust the weighting given to a particular pseudospecies, for instance to give it double the weighting, simply enter '2' into the relevant box, leaving the other boxes at '1'.
Indicator levels. Defines which pseudospecies cut levels can act as indicators. The default is all; to deselect a level, uncheck a box.
Output from TWINSPAN is presented on a series of tabbed pages. These are described in turn: