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+.. table::
+ :widths: 30 50 20
+
+ +-----------------------------------------------------------------+----------------------------------------------------------------------+------------------------------------------------------------------+
+ | .. figure:: | A Frechet mean (or barycenter) is a generalization of the arithmetic | :Author: Theo Lacombe |
+ | ./img/barycenter.png | mean in a non linear space such as the one of persistence diagrams. | |
+ | :figclass: align-center | Given a set of persistence diagrams :math:`\mu_1 \dots \mu_n`, it is | :Introduced in: GUDHI 3.1.0 |
+ | | defined as a minimizer of the variance functional, that is of | |
+ | Illustration of Frechet mean between persistence | :math:`\mu \mapsto \sum_{i=1}^n d_2(\mu,\mu_i)^2`. | :Copyright: MIT |
+ | diagrams. | where :math:`d_2` denotes the Wasserstein-2 distance between | |
+ | | persistence diagrams. | |
+ | | It is known to exist and is generically unique. However, an exact | |
+ | | computation is in general untractable. Current implementation | :Requires: Python Optimal Transport (POT) :math:`\geq` 0.5.1 |
+ | | available is based on [Turner et al, 2014], and uses an EM-scheme to | |
+ | | provide a local minimum of the variance functional (somewhat similar | |
+ | | to the Lloyd algorithm to estimate a solution to the k-means | |
+ | | problem). The local minimum returned depends on the initialization of| |
+ | | the barycenter. | |
+ | | The combinatorial structure of the algorithm limits its | |
+ | | scaling on large scale problems (thousands of diagrams and of points | |
+ | | per diagram). | |
+ +-----------------------------------------------------------------+----------------------------------------------------------------------+------------------------------------------------------------------+
+ | * :doc:`barycenter_user` | |
+ +-----------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+