Remove specific rows from matrix

I have two matrices shown below:

A =

    0.2247    0.5845
    0.4942    0.7303
    0.5000    0.5000
    0.6440    0.5408
    0.6210    0.2230
    0.6210    0.2230
    0.2869    0.3921
    1.0000    1.0000
    
B =

    0.2247    0.5845
    0.4942    0.7303
    0.6440    0.5408
    0.6210    0.2230
    0.2869    0.3921

I would like to delete the rows in matrix A that match the rows from matrix B. How would I go about doing this?

Thanks in advance.

Answer 1

[Adam Danz]

If you're looking for exact matches use

Lia = ismember(A,B,'rows')

However, with floating decimals it's likely that your variable values may differ slightly such as 0.28690123 vs 0.28690131. If you'd like that to be considered a match, use

LIA = ismembertol(A,B,tol,'ByRows',true)

To identify and remove the first match of B within A,

removeRowIdx = cell2mat(arrayfun(@(i) find(ismember(A,B(i,:),'rows'),1,'first'),(1:size(B,1))','UniformOutput',false)); 
A(removeRowIdx,:) = []

[John D]

Thanks, I'd be looking for exact matches.

I wanted this to find and remove only the first occurrence of each. Would this do that, or remove all occurrences? I've updated the example data.

[Adam Danz]

Hi John, I added two lines to the end of my answer that identifies and removes only the first matching row. This uses ismember() so the match must be a perfect match. With floating decimals you may want to use ismembertol() instead if you find that number that seem like perfect matches aren't being matched.

[John D]

Thanks, that helps

[Adam Danz]

Glad I could help!