Extended Functions of SweepLine.py
unix$ SweepLine.py data.txt -D --makeimage unix$ ds9 data_image.fits -region data_points.reg -region data_Delaunay.reg
With the "--calarea" option, SweepLine.py calculate the area of each Voronoi cell and save the value in an "area map".
unix$ SweepLine.py data_image.fits --calarea unix$ ds9 data_image_area.fits -region a.reg -region data_image.reg
The sum of the area values in each cell is 64 (8x8).
Build Pixelated Voronoi Diagram (image input only)
Pixelation of the Voronoi diagram is sometimes useful, which provides you an image mask of the Voronoi tessellation. While building this pixelated Voronoi diagram (PVD), all the pixels enclosed by a Voronoi cell are included into a pixelated Voronoi cell. If one pixel is equally distant from two or more Voronoi sites (i.e., the pixel center falls on an Voronoi edge), it is assigned randomly among the two or more cells. The option is "--calpvd"
unix$ ./SweepLine.py data_image.fits --calpvd unix$ ds9 data_image_pvd.fits -region data_image.reg
Generate a density map (image input only)
Density is defined as pixel value divided by cell area. With the "--caldst" option, SweepLine.py fills a PVD with the density value. This provides kind of a dynamical-scale smoothing.
unix$ ./SweepLine.py data_image.fits --caldst unix$ ds9 data_image_dst.fits -region data_image.reg
Note that some on-Voronoi-edge pixels are assigned randomly to a related cell. The density value of such pixel is not randomly selected, it's calculated by averaging the nearest pixels around it.
You can manually set the image sizes with this options. The sizes must be larger than the shifted points coordinates.
unix$ ./SweepLine.py data.txt --size "10,15" --makeimage unix$ ds9 data_image.fits -region data.reg -region data_points.reg
Remove points at the image border from the area map. See the example area maps of one same image including and excluding these points. It's clear why these points are useless. Their areas can be enlarged manually with the "--size" option.
--resolution N [0~5] default=3
When you input points as events, the positions, which are regarded as image coordinates by SweepLine.py, can be float value with high accuracy. However it's unpractical if the accuracy is too high. With the "--resolution N" option, the float coordinates will be rounded to N decimal places.
unix$ cat data.txt -0.5 1.5 1.1 3.3 2.9 5.7 3.1 4.3 5.4 2.6 6.3 3.1 6.3 3.1001 unix$ SweepLine.py data.txt --resolution 3 Voronoi Construction: data Warning: 1 duplicated points deleted >> data.reg unix$ SweepLine.py data.txt --resolution 4 Voronoi Construction: data >> data.reg
In this example, we add a point "6.3 3.1001" to the end of data.txt. Using --resolution 3, this point will be excluded. While using --resolution 4, it is treated as an independent point.