# How to make a new matrix with all common arrays from different matrices

1 view (last 30 days)
Moe on 11 Nov 2014
Edited: Andrei Bobrov on 12 Nov 2014
Suppose I have some matrices as follow:
m1 = [1;2;3;4;5;6;7;8];
m2 = [2;3;4;6;7;8;9;10;11;12];
m3 = [4;5;6;7;8;9;1;;16];
m4 = [8;8;5;4;3;1;6;7];
I need a matrix which is included all common arrays in all matrices, such as:
m = [4;6;7;8];

Azzi Abdelmalek on 11 Nov 2014
Edited: Azzi Abdelmalek on 11 Nov 2014
m1 = [1;2;3;4;5;6;7;8];
m2 = [2;3;4;6;7;8;9;10;11;12];
m3 = [4;5;6;7;8;9;1;;16];
m4 = [8;8;5;4;3;1;6;7];
a=intersect(m1,m2)
b=intersect(m3,m4)
out=intersect(a,b)
Azzi Abdelmalek on 12 Nov 2014
Sorry
m1 = [1;2;3;4;5;6;7;8];
m2 = [2;3;4;6;7;8;9;10;11;12];
m3 = [4;5;6;7;8;9;1;;16];
m4 = [8;8;5;4;3;1;6;7];
m={m1,m2,m3,m4}
a=m{1}
for k=2:numel(m)
a=intersect(a,m{k})
end

Star Strider on 11 Nov 2014
Edited: Star Strider on 12 Nov 2014
I donâ€™t know why you have to use a cell array, but then Iâ€™m only slightly familiar with what youâ€™re doing.
Using eval is not considered good programming style, but this code may work for you. (It does do what you want.) You can make â€˜Mâ€™ a cell array if you like, but keeping it numeric might be better:
m1 = [1;2;3;4;5;6;7;8];
m2 = [2;3;4;6;7;8;9;10;11;12];
m3 = [4;5;6;7;8;9;1;;16];
m4 = [8;8;5;4;3;1;6;7];
n = 4;
M = m1;
for k1 = 2:n
M = intersect(M,eval(['m' num2str(k1)]));
end
See if it works for you.
Star Strider on 12 Nov 2014
My pleasure!
I’m not certain that I understand exactly what you’re doing, but if you’re naming your vectors ‘m1’...‘m4’, use the code in my original answer (the eval loop) will sort them and take their intersections automatically.
You can wrap them in a function:
function M = vctintsct(m1,m2,m3,m4)
n = 4;
M = m1;
for k1 = 2:n
M = intersect(M,eval(['m' num2str(k1)]));
end
end
This works if you always have four vectors (you can name them anything in this instance, since the function will name them ‘m1’ etc.), then simply call the function as:
M = vctintsct(m1,m2,m3,m4);
and get ‘M’ as the output. It is a double-precision vector, but you can then assign it as an element of a cell array in your main script. If you have varying numbers of vectors, the function gets a bit more complicated but will still work.

Andrei Bobrov on 12 Nov 2014
Edited: Andrei Bobrov on 12 Nov 2014
m1 = [1;2;3;4;5;6;7;8];
m2 = [2;3;4;6;7;8;9;10;11;12];
m3 = [4;5;6;7;8;9;1;;16];
m4 = [8;8;5;4;3;1;6;7];
MM = {m1,m2,m3,m4};
z = cat(1,MM{:});
[a,~,c] = unique(z);
nn = cellfun(@numel,MM);
ii = accumarray(cumsum([1,nn])',1);% Idea by Roger Stafford
ii = cumsum(ii(1:end-1)); %
out = a(all(accumarray([c,ii],1),2));

### Categories

Find more on Matrix Indexing in Help Center and File Exchange

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by