This repository contains code & data for our publication “Persistence Concepts for 2D Skeleton Evolution Analysis”, which was accepted for the conference Topology-Based Methods in Visualization 2017.

At present, the code is rather unstructured. Expect additional instructions soon.

Our analysis always has the same basic steps:

• Extract skeletons (this is not done by the code in this repository!)
• Obtain bipartite matches
• Analyse those bipartite matches in order to obtain consistent creation times for every pixel in the skeletons
• Calculate persistence-based concepts, such as age persistence, from the analysed matches

To obtain the matches, use the make_assignments script:

$ ./make_assignments.py Simulation/Simulation_??.txt

Copy the resulting files Matches_*_*.txt to another folder. Next up, we process the matches:

$ ./process_matches.py Simulation/Matches/Matches_*.txt

This will create a set of directed matches, which is required for the subsequent analysis and propagation of creation times. The propagation of creation times is achieved via the following:

$ ./analyse_bipartite_matches_new.py --width 1500 --height 1000 Simulation/Matches/*.txt > Ages_simulation.txt

Note that the script requires that you supply the width and height of the input data. This is necessary in order to figure out neighbourhoods in the skeleton. Afterwards, use the split_output.py utility script from Aleph, available in the repository of Aleph, to split the output file into smaller files:

$ ./split_output.py --start=2 --prefix=t Ages_simulation.txt

You should now have a list of files, each corresponding to a given time step, with consistent creation times. As a last step, you can create persistence diagrams by issuing the following command:

$ ./make_persistence_diagrams.py --width 1000 --height 1500 --prefix=Simulation_ --path Simulation Ages_t??.txt

The path and prefix parameters are required so that the script knows where to find the skeletons. This will place a set of files in /tmp:

/tmp/t*_age_persistence.txt:                age persistence values on the skeleton (x,y,p), with p denoting the persistence
/tmp/t*_branch_persistence.txt:             ditto for branch persistence
/tmp/t*_growth_persistence.txt:             ditto for growth persistence
/tmp/t*_segment_branch_persistence_max.txt  age persistence diagram (incorrectly named maybe)
/tmp/t*_segment_branch_persistence_min.txt  branch persistence diagram 

From this, various statistics, such as the vivacity of a process, can be calculated. This is not (yet) documented, but please take a look at the Makefile and the other scripts for more details.

Please contact the corresponding author for more information.