Consider the inner product space $(\mathbb{R}^n, \langle\cdot,\cdot\rangle)$ and suppose that there are one-dimensional orthogonal subspaces $\{V_i\}_{i=1}^n$ such that $\mathbb{R^n} = \oplus_{i=1}^n V_i$.
Now suppose that you observe data $X \subseteq \mathbb{R}^n$, and each data point belongs to one of the $n$ subspaces. The aim is to group the data into $n$ clusters, one cluster for each subspace. Are there any efficient algorithms to determine such clustering?
The figure below shows an example of a clustering when $n=2$: