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RE: Intersection of 2 subspaces

• To: mathgroup at smc.vnet.net
• Subject: [mg21694] RE: [mg21681] Intersection of 2 subspaces
• From: "Ingolf Dahl" <f9aid at fy.chalmers.se>
• Date: Sat, 22 Jan 2000 02:52:56 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

If your vector sets are set1 and set2, try with

NullSpace[Join[NullSpace[set1], NullSpace[set2]]]

Ingolf Dahl
Chalmers University
f9aid at fy.chalmers.se

-----Original Message-----
From: RENAULT Fabien [mailto:renaulf1 at cti.ecp.fr]
To: mathgroup at smc.vnet.net
Subject: [mg21694] [mg21681] Intersection of 2 subspaces


Here is my problem :
In a vectorial space of dimension n, I have 2 different subspaces defined
by a set of vectors. I need to find the subspace intersection of those 2
subspaces that is to say find the vectors directors that define the
subspace intersection.


For example if n=4 
If my first subspace is defined by the vectors (0,0,0,1) and (0,0,1,0)
If my second subspace is defined by the vectors (1,0,0,0) and (0,0,1,1)

Then the answer would be the subspace intersection defined by the vector
(0,0,1,1).

If someone could tell me where to find such a function or how to build an
efficient algorithm that could handle much higher values of n (up to
25-30) that would be a great help for me.

Thanks