How to check if all rows of a matrix are equal
You can use: are all components of all rows equal to the first row?
allRowsEqual = all(all(bsxfun(@eq, A, A(1,:))));
On the other hand, you can use a simple loop faster for
, since the above will need to look at the whole matrix ...
allRowsEqual = true;
for k = 1:size(A,1)
if any(A(k,:)~=A(1,:))
allRowsEqual = false;
break;
end
end
If you want to go for clarity, it basically says: is there only one unique string?
allRowsEqual = size(unique(A,'rows'),1)==1;
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Find the difference between consecutive elements in columns
c and then determine if all such differences are zeros in c , giving us a simple one-way and very efficient solution - diff(..,1)
nnz(..)==0
isallrowsequal = nnz(diff(A,1))==0 %// A is input matrix
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Another method I can suggest is to use ismember
and check if all values are in the resulting vector 1
:
allRowsEqual = all(ismember(A, A(1,:), 'rows'));
As ismember
works for a flag rows
, this will output a vector logical
where 1
will denote the lines A
that match A(1,:)
(or the first line A
) and 0
otherwise. To make sure all rows are the same, you just need to check if all the values in this logical
vector are not 1
, and if this is the case, then every row in your matrix is equal to each other.
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you can check this for example:
suppose you have two matrices a and b;
a =
1 2 3
4 5 6
7 8 9
b =
1 4 7
2 5 8
3 6 9
you can check if the matching strings are equal using "sum":
sum(a-b) ans = 6 0 -6
but if you try it for two equals, you will have all columns of the resulting vector equal to zero:
sum(a-a) ans = 0 0 0
then you can check if the resulting vector is equal to a vector of zeros of the same size.
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