DREiMac is a library for topological data coordinatization, + visualization, and dimensionality reduction. Currently, DREiMac is + able to find topology-preserving representations of point clouds + taking values in the circle, in higher dimensional tori, in the real + and complex projective spaces, and in lens spaces.
+In a few words, DREiMac takes as input a point cloud together with + a topological feature of the point cloud (in the form of a persistent + cohomology class), and returns a map from the point cloud to a + well-understood topological space (a circle, a product of circles, a + projective space, or a lens space), which preserves the given + topological feature in a precise sense.
+DREiMac is based on persistent cohomology
+ (
The documentation for DREiMac can be found
+
Topological coordinatization is witnessing increased application in
+ domains such as neuroscience
+ (
To the best of our knowledge, the only publicly available software
+ packages implementing cohomological coordinates based on persistent
+ cohomology are Dionysus
+ (
DREiMac adds to the current landscape of cohomological coordinates + software by implementing various currently missing functionalities; we + elaborate on these below. DREiMac also includes functions for + generating topologically interesting datasets for testing, various + geometrical utilities including functions for manipulating the + coordinates returned by the algorithms, and several example notebooks + including notebooks illustrating the effect of each of the main + parameters of the algorithms.
+The circular coordinates algorithm turns a cohomology class with
+ coefficients in
Parametrizing the circularity of a trefoil knot in 3D.
+ Here we display a 2-dimensional representation, but the
+ 3-dimensional point cloud does not have self intersections (in the
+ sense that it is locally 1-dimensional everywhere). On the right,
+ the output of the circular coordinates algorithm without applying
+ the algebraic procedure to fix the lift of the cohomology class. On
+ the left, the ouput of DREiMac, which implements this fix. Details
+ about this example can be found in the documentation.
+
Another practical issue of the circular coordinates algorithm is
+ its performance in the presence of more than one large scale circular
+ feature (Figures
+
Parametrizing the circularity of a surface of genus two
+ in 3D. Here we display a 2-dimensional representation, but the
+ 3-dimensional point cloud does not have self intersections (in the
+ sense that it is locally 2-dimensional everywhere). This is
+ DREiMac’s output obtained by running the toroidal coordinates
+ algorithm. The output of running the circular coordinates algorithm
+ is in Figure
+
Parametrizing the circularity of a surface of genus two
+ in 3D. This output is obtained by running the circular coordinates
+ algorithm. The parametrization obtained is arguably less
+ interpretable than that obtained by the toroidal coordinates
+ algorithm, shown in Figure
+
We illustrate DREiMac’s capabilities by showing how it parametrizes
+ the large scale circular features of the unprecessed COIL-20 dataset
+ (
Persistent cohomology of 5 clusters of unprocessed
+ COIL-20 dataset.
+
We use single-linkage to cluster the data into 5 clusters and
+ compute the persistent cohomology of each cluster. We then run the
+ circular coordinates algorithm on each cluster, using the most
+ prominent cohomology class of each cluster. We display the result in
+ Figure
+
Unprocessed COIL-20 parametrized by clustering and
+ circular coordinates.
+
J.A.P.: initial MATLAB implementation (not part of this software) + and design of this software. C.T. and L.S.: design and + implementation.
+We thank Tom Mease for contributions and discussions. J.A.P. and + L.S. were partially supported by the National Science Foundation + through grants CCF-2006661 and CAREER award DMS-1943758.
+