Delete row from matrix given an id- Matlab
How can I delete a certain row from a matrix depending on the 1st column value?
For example: A=[1 2 3;3 4 5;5 6 7] where the values of the first column represent the ids and I want to delete the row that has 5 as an id. I already know that A(3,:)= deletes the third row, but what if I have the id and don't know the row number?
You can use find:
id=5; A(find(A(:,1)==id),:)= A = 1 2 3 3 4 5
Note that, as mentioned by Divakar, thanks to logical indexing you can even omit the find:
A(logical([0 0 1]),:)
are equivalent so
will give the same result.
If you have only element as id, then I would go with @yoh.lej's solution. But, if you happen to have an array of elements as id, you can use one of the approaches listed next.
Approach # 1 (With ismember)
A(ismember(A(:,1),ids),:) = ;
Approach # 2 (With bsxfun)
A(any(bsxfun(@eq,A(:,1),ids(:)'),2),:) = ;
If the first column of A has unique ids, then you have two more approaches to play with.
Approach # 3 (With intersect)
[~,remove_rowid] = intersect(A(:,1),ids); A(remove_rowid,:) = ;
Approach # 4 (With setdiff)
[~,select_rowid] = setdiff(A(:,1),ids,'stable'); A = A(select_rowid,:);