Pulling subset from a 2D matrix

Hi,

I am struggling how to extract part of a 2D matrix based on logical criteria:

example:

a=[1 1 1 ; 2 2 2 ; 3 3 3]
b=a<3  % let say I want to have the subset where a<3
mySubset=a.*b

how can I obtain the subset using logic and not having a line of zeros where a=3?

Thanks

Answer 1

[Azzi Abdelmalek]

a=[1 1 1 ; 2 2 2 ; 3 3 3]
b==a<3
mySubset=a.*b

[Simon]

Thanks for the answer, however, the resulting subset is still of the same dimension as "a". I would like to end up in this example with a matrix containing only 1 and 2, meaning a 2*3 matrix.

[Azzi Abdelmalek]

a=a(all(a<3,2),:)

[Simon]

Thanks! I was not aware of the function all()

[Roger Stafford]

The 'all' method only works if all elements of a row in 'a' are less than 3. In general I think what you really want is

 mySubset = a(b);

The result will be a one-dimensional array but in the general case that is unavoidable.