Viewing Matrices in Different Dimensions

Although ViewHAR will read real matrices of up to 7 dimensions, only 2-dimensional items may be shown on the screen, exported, or printed. Higher dimensional matrices must be reduced to 2 dimensions either by summing over one or more dimensions, or by selecting individual 'slices' for viewing.

For example, if a 3-dimensional matrix is selected for viewing, it may first appear as a matrix of subtotals, summed over the 3rd dimension. Three combo boxes will appear at the right hand side of the tool bar, indicating that the screen displays ALL of dimensions 1 and 2 and the SUM over dimension 3. This will also be indicated in the status bar at the bottom of the screen: the 'hidden' dimensions of the matrix are enclosed in square brackets.

The following combo boxes indicate that a 26 x 25 x 2 matrix is currently shown as a 26 x 25 matrix of subtotals over the 3rd dimension.

pic00002

You could alter the combo boxes to view a 3-dimensional matrix in other ways. For example, you could sum over the 1st dimension instead of the 3rd. As well as summing, you can reduce dimensionality by 'slicing': choosing to display one element only in some dimension. This is the only way to see individual elements of a many-dimensional matrix. To see only element 1 of the third dimension, the third of the combo boxes above would be altered as follows:

pic00003

If the 'ALL' option is selected for more than 2 combo boxes, the resulting matrix will have more than 2 dimensions and so cannot be displayed. Usually in that case a warning box will appear, inviting you to aggregate or slice in another dimension.

However, the File..Options menu offers an 'AutoAggregate' option (by default not selected) which allows you to modify the above behaviour. If AutoAggregate is selected, then, if  you alter one aggregation combo box so that the 'ALL' option is selected for more than 2 dimensions, ViewHAR will set the rightmost of the other ALL combo boxes to Sum (so that the display is 2-dimensional).  

For RE type real matrices of >2 dimensions, row and column labels will be displayed (if available) only for those dimensions for which the corresponding combo box has been set to 'All'.


URL of this topic: www.copsmodels.com/webhelp/viewhar/hc_agg.htm

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