Manifold Clustering
Richard Souvenir and Robert Pless
Washington University in St. Louis
Department of Computer Science and Engineering
Campus Box 1045, One Brookings Drive, St. Louis, MO 63130
{rms2, pless}@cse.wustl.edu
Abstract
Manifold learning has become a vital tool in data driven
methods for interpretation of video, motion capture, and
handwritten character data when they lie on a low dimen-
sional, non-linear manifold. This work extends manifold
learning to classify and parameterize unlabeled data which
lie on multiple, intersecting manifolds. This approach sig-
nificantly increases the domain to which manifold learn-
ing methods can be applied, allowing parameterization of
example manifolds such as figure eights and intersecting
paths which are quite common in natural data sets. This
approach introduces several technical contributions which
may be of broader interest, including node-weighted multi-
dimensional scaling and a fast algorithm for weighted low-
rank approximation for rank-one weight matrices. We show
examples for intersecting manifolds of mixed topology and
dimension and demonstrations on human motion capture
data.
1. Introduction
Data-driven modeling is a powerful approach for non-
rigid motion analysis. Manifold learning approaches have
been applied to automatically parameterize image data sets
including head pose, facial expressions, bird flight, MR im-
agery, and handwritten characters. Each of these data sets
lies on low-dimensional manifolds that are not linear sub-
spaces of the (high-dimensional) input data space. Manifold
learning approaches seek to explicitly or implicitly define
a low-dimensional embedding of the data points that pre-
serves some properties (such as geodesic distance or local
relationships) of the high-dimensional point set.
When the input data points are drawn from multiple
(low-dimensional) manifolds, many manifold learning ap-
proaches suffer. In the case where the multiple mani-
folds are separated by a gap, techniques such as isomet-
ric feature mapping (Isomap) [15] may discover the dif-
Figure 1. For high-dimensional data points
which lie on intersecting low-dimensional
manifolds, manifold embedding techniques
benefit from first separating points into dis-
tinct classes. These toy problems illustrate
relevant cases. (left) The spirals data set,
which can be embedded in two dimensions
with minimal error, can also be embedded
as two one-dimensional manifolds. (right)
The circle-plane data set includes component
manifolds of different dimension. The seg-
mentations shown here by the different sym-
bols are automatically determined by the ap-
proach developed in this paper.
ferent manifolds as different connected components in the
local neighborhood graph, and spectral clustering tech-
niques may identify and cluster each manifold based on
the optimization of certain objective functions. However,
if there is significant overlap in the manifolds, prior meth-
ods fail in one of two ways: either, in the case of Isomap,
from the non-existence of a low-dimensional embedding
which exactly (or nearly) preserves properties of the high-
dimensional manifold, or, in the case of Locally Linear Em-
bedding (LLE) [13] or Semidefinite Embedding (SDE) [16],
from the fact that additional work is necessary to interpret
R. Souvenir and R. Pless, Manifold Clustering, in Proceedings of the 10th International Conference on Computer Vision (ICCV 2005),
Beijing, China, October 2005, pp. 648 – 653.