How to convert a specific column to unit vector.

Let's say i have the following matrix [1 2 3 4; 5 6 7 8; 9 10 11 12]

For a certain condition, "6" satisfies the condition. Now i want to make the 2 column in which 6 is present a unit vector. I am able to do it for one iteration by manually coding the row operations but if the next element that satifies the condition happens to be in (3,1).

How to create a macro of sorts to solve this in MATLAB. Appreciate the help. Thanks

[Walter Roberson]

     1     2     3     4
     5     6     7     8
     9    10    11    12

has 6 only in 1 column.

Are you trying to produce the vector [2;6;10] or the vector [5 6 7 8]? Or something else?

[Yuvaraj Pazhamalai]

I want the column to be converted into an unit vector.

[Walter Roberson]

Do you mean like [2;6;10] / norm([2;6;10]) ? "unit vector" in the sense that the sum of the squares of its components is 1.0 ?

[Yuvaraj Pazhamalai]

No, not really. i want row operations to be done on the entire matrix so that the 2nd column become [0 1 0] and the other columns will change corresponding to the row operations.

Answer 1

[Walter Roberson]

If you have a vector V that you want to convert to a "unit vector" in the sense that the magnitude of the unit vector is 1.0, then

unit_V = V/.norm(V);

[Yuvaraj Pazhamalai]

Sorry, this is not what i wanted. I want the row operations like the following: R2=R2/6 R1 = R1-2*(R2/6) etc.

[Walter Roberson]

In order to hope to be able to do that, you would have to write a MATLAB class that implemented all of the operations. I am not certain that it can be done at all: the one operation that cannot be overridden in MATLAB is assignment, so R2 = R2/6 would not be able to associate the destination "R2" with the original matrix.

It would be easier if you could accept a syntax such as

M.R2 = M.R2/6;
M.R1 = M.R1 - 2*(M.R2/6);

then this could be coded as getting or setting properties of the object M with the object M retaining its type.

Setting all of this up would certainly take more effort than just using normal matrix indexing,

M(2,:) = M(2,:)/6;
M(1,:) = M(1,:) - 2*(M(2,:)/6);