Delete multiple rows from array

I need to delete multiple rows from an array. I know I cannot use a loop because the size of the array will change.

Does anyone have any suggestions on how to accomplish this?

UPDATED: For example, if I have an array such as:

1 9 0

2 1 2

5 8 3

7 1 0

Depending on if the 3rd column is a 0 (I used num2cell, so I'm not sure what type that makes each item in the cells), then I want to delete the whole row. So in the above example,

1 9 0

7 1 0

Would both be deleted, and the array would then only be a 2x3 array.

Thanks in advance! Let me know if I need to add more details. -Matt

[the cyclist]

Could you give more detail on what your array looks like (or, ideally, a small example)? Is "array" really a cell array, as the comment suggests? If so, then it seems that v1,v2 and v3 are also cell arrays. If that's the case, then what's inside the cells?

[Sean de Wolski]

might want to look at ismember() to build up your index2delete vector

Answer 1

[per isakson]

Two possible approaches are:

array( v3==0, : ) = [];

and

for ii = size( array, 1 ) : -1 : 1
    if v3{ii}==0
        array( ii, : ) = [];
    end
end

Loop from bottom up seems to be the simplest way, if the array is not too big.

========================= UPDATE

Yes, it is possible to use v3. However, it "smells". My point was to loop from bottom up, which I thought was appropriate to point out since you excluded looping.

The code below does what I think you are asking for

num = [
     1     9     0
     2     1     2
     5     8     3
     7     1     0 ];

cac = num2cell( num );
ca1 = cellfun( @(x) num2str(x), cac, 'uni', false );  
iscellstr( ca1 )
ca2 = ca1;
for ii = size( ca1, 1 ) : -1 : 1
    if strcmp( ca1(ii,3), '0' )
        ca1( ii, : ) = [];
    end
end
ca2( strcmp( ca2(:,3), '0' ), : ) = [];
strcmp( ca1, ca2 )
all( strcmp( ca1, ca2 ) )
all( all( strcmp( ca1, ca2 ) ) )

[Matt]

Is it still possible to reference v3 after it has been added into the array?

Either way, when I try this I get this error:

"Undefined function 'eq' for input arguments of type 'cell'."

I have chars in the cell, so I cannot simply use 0.

Thanks for the quick response!

[Matt]

Actually, it will be easier to think of my array as only a two dimensional array, so it is structured like

1 9 0

2 1 2

5 8 3

7 1 0

And depending on if the 3rd column is a 0 (I used num2cell, so I'm not sure what type that makes each item in the cells), then I want to delete the whole row.

So in the above example,

1 9 0

7 1 0

Would both be deleted, and the array would then only be a 2x3 array.

Thanks!

-Matt

[per isakson]

I'm still not sure whether you want to compare double or characters.

[Matt]

This is what I was looking for! Thanks for your help! I shouldn't have disregarded loops as you said. This worked great, thanks again!

-Matt

Answer 2

[prasoon purwar]

    if isequal(v3,0)==1
    array(n,:)=[]
     end % array is your matrix
         % n is the row , which is to be removed

[Matt]

Should I do this inside of a loop? As I said above, can I still access v3 by name after it has been pushed into array?

Thanks for the quick response!