# normalizing constant of a column

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Melissa on 5 Jul 2013
Good Morning All,
Probably one of the most simplest questions I have ever asked but when normalizing the first column of a matrix its simple just the square root of the sum of the elements of the column squared correct?
I have a torque roll axis direction defined as a normalizing constant, a, for the first column of matrix: a*J=M^-1
I have the mass matrix and need to find J and a. I am assuming that I am dividing inv(M) by a. and that a is the sqrt of the sum of the squares of inv(M).
Is this correct?
Thanks a bunch.

Matt J on 5 Jul 2013
Edited: Matt J on 5 Jul 2013
when normalizing the first column of a matrix its simple just the square root of the sum of the elements of the column squared correct?
It's correct assuming you want the Euclidean norm of the column set to 1. But there are other norms, so it really depends on what you're doing,e.g.
>> v=[1 2 3];
>> v/norm(v)
ans =
0.2673 0.5345 0.8018
>> v/norm(v,1)
ans =
0.1667 0.3333 0.5000
>> v/norm(v,inf)
ans =
0.3333 0.6667 1.0000
Matt J on 5 Jul 2013
Yes.