8 Displaying a Slice

This network displays a two-dimensional slice through a data cube, parallel to two of the axes. The slice is plotted as a false colour array shown in its correct relative position inside a set of axes representing the edges of the data cube. Note that the colour table for converting data values into displayed colours is derived from the range of values in the entire data cube, not just the slice being plotted, in order to facilitate the comparison of several slices.

8.1 Use

The network is shown in Figure 11.

Figure 11: Network to display a slice through a data cube.

• To specify the data cube to be read double-click on the ‘Import’ module and follow the instructions in Section 4.1.
• To specify the axis to which the slice is perpendicular double-click on the left-hand of the two ‘Integer’ modules at the top of the network. The permitted values are 0, 1 and 2 for the $x,y$ and $z$ axes respectively.
• To specify the slice which is to be extracted double-click on the right-hand of the two ‘Integer’ modules at the top of the network. For a cube with $n$ elements along the chosen axis the permitted values are 0 to $n-1$.

8.2 Notes

Module ‘ShowBox’ extracts the bounding box of the data cube. ‘Slab’ extracts the specified slice. ‘Statistics’ finds the minimum and maximum values in the cube; they are used by ‘AutoColor’ to generate a false colour image of the extracted slice. ‘Collect’ combines the bounding box and extracted slice.

8.3 Alternatives

If your data are in Starlink NDF format then an alternative way to plot a slice is to use command DISPLAY in KAPPA (see SUN/95[8]). You simply specify the required slice, for example:

plots the twenty-first slice in the third axis.