# subspace

## Purpose

Angle between two subspaces.

## Synopsis

    t = subspace(A,B)

## Description

`t = subspace(A,B)` finds the angle between two subspaces specified by the columns of `A` and `B`. If `A` and `B` are vectors of unit length, this is the same as `acos(A'`*`B)`.

## Examples

If the angle between the two subspaces is small, the two spaces are nearly linearly dependent. In a physical experiment described by some observations `A`, and a second realization of the experiment described by `B`,`subspace(A,B)` gives a measure of the amount of new information afforded by the second experiment not associated with statistical errors of fluctuations.

For example, consider a study that requires two groups of medical patients, a control group and a test group. Assume that data exists for several groups of patients, and this data is organized into one matrix per group. Each row of a matrix represents various test results for a single patient. The two groups with the smallest returned `angle` are the most similar with regard to these test results.

(c) Copyright 1994 by The MathWorks, Inc.