The Preferences dialog window allows you to set user-default values for some GS+ behaviors. There are three categories available – settings for Analyses (as described here), settings for Data File Import, and settings for General Preferences.
The Reset command returns all user-default values on this tab only to original (GS+ - defined) default values. To reset all values on all tabs, use the Global Reset command.
• Offset start of first lag by ½ interval – with this check box GS+ will (when automatically defining uniform interval lag classes) shift the first lag class to ½ of its normal separation distance. This can provide better resolved variograms when there are sufficient pairs of points in shorter separation distance classes. The disadvantage is that if there are few pairs of points for the shortest distance classes when the first lag is not offset (a common problem), there will be even fewer pairs available with the first lag offset. If this is the case, there will be little if any improvement to the variogram.
• Active lag (% of maximum) – the default active lag size is 50% of the maximum possible unless a different percentage is specified here.
• Automatically make anisotropic surface map – the Surface Map command on the Autocorrelation Window will be automatically pressed after variograms are calculated. This may make your exploration of anisotropic relationships easier but there is a performance penalty as creating a surface map requires further computation.
• Number of lag intervals – the default number of lag intervals is 15 unless changed here. The lag interval or step size will thus be equal to the active lag distance divided by number of lag intervals.
• Automatically subsample large data sets – very large data sets can take hours of cpu time under certain conditions. Check this box to randomly subsample the data set during autocorrelation analysis only. When this box is checked and the data set being analyzed has more than the specified number of subsamples, only that number of subsamples are used in the autocorrelation analysis.
Locations used in the analysis are randomly selected, and each subsampled location is compared against every other location in the data set regardless of whether the other location was also selected as a subsample – in this way there is no bias against small distance intervals due to subsampling. As an example of the time savings possible, 10,000 subsamples of a 160,000 point data set took 10 cpu minutes to produce essentially the same semivariogram model that otherwise took >8 cpu hours. Each of the 10,000 subsampled points was compared to the 159,999 other points to produce the variogram, as opposed to when the full data set was sampled by comparing each of 160,000 points to 159,999 other points.
• Number of subsamples – specify the number of data records to use when subsampling large data sets.
• Weighting Power (0-100) – this value provides the initial default weighting power for inverse distance weighting (IDW) interpolation. This value may be overridden from the Interpolate Window; see the Interpolate Window for further information on this parameter.
• Smoothing Factor (>0) – this value provides the initial default smoothing factor for inverse distance weighting (IDW) interpolation. This value may be overridden from the Interpolate Window; see the Interpolate Window for further information on this parameter.
• Default to Normal Distance Weighting (NDW) – sets the default IDW interpolation to Normal Distance Weighting (NDW). This value may be overridden from the Interpolate Window; see the Interpolate Window for further information on this parameter.
• Draw map after interpolating – check this box to automatically draw the map of interpolated values after interpolation.
• Use different seed – when this box is checked simulations will be started with a different random number seed, which means the random path through the simulation will be dissimilar.
• Suse multigrid refinements – Check this box to automatically use multgrid refinements.
• Number of simulations – set the default number of simulations to perform..
• Draw map after interpolating – check this box to automatically draw the map of interpolated values after interpolation.
• Report std deviation (not variance) – check this box to report standard deviation values rather than variance values for interpolation error terms. This is a default condition that can be changed in the Interpolation Window.
• Cycle faster on x than y – ordinarily 2-dimensional interpolation results are written to output files with y-coordinate values cycling fastest (e.g. in the x,y order 10, 2; 10, 3; 10, 4; 10, 5; 20, 2; 20, 3; 20, 4, 20, 5); check this box to write results with x-coordinate values cycling faster (e.g. 10, 2; 20, 2; 10, 3; 20, 3; 10, 4; 20, 4; 10, 5; 20, 5).
Sets all user-default values on all tabs to original (GS+ defined) default values.
Cancel preference changes and close window.
Close window and keep preference changes.