# 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?

## Answers

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(3,:)

and

A(logical([0 0 1]),:)

are equivalent so

A(find(A(:,1)==id),:)=[]

and

A(A(:,1)==id,:)=[]

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,:);