MATLAB: Elemental subtraction indices of initial vector

bsxfunelementalfindindicessubstracting

Hi !

A is my array of numbers

I substract all the elements from each other with A – A' which give me a matrice T with size of length (A) * length (A)

Now that I want to look for specific value in this matrice, find (T == x) it gives me the indices of the value in the matrice.

My question is how can I find out what this indece represents in form of my initial array A?

in short :::

T = A – A '

find (T == my value) ==> ans = i where T (i) == my value

how to find out j and k where T (i) = A (j) – A (k)

Thanks in advance!

Best Answer

A = [1 2 1 2 2 3 4 5] ;
T = A-A.' ; 
x = 0 ; 
idx = T == x ; % get logical indices 
[r,c] = ind2sub(size(T),find(idx))  % get row and column positions

Related Solutions

MATLAB: If else statement for elemental comparison

The logical indexing shouldn't be used in combination with an if-statement. Let me give you a small example:

a=[3 5 6];
b=[5 4 8];
%then a>b results in [false true false] (or [0 1 0])
%a([0 1 0]) is 5, so a(a>b) is 5
%a(a<b) is [3 6]

That is called logical indexing, because you use a logical array to index another array.

The code below should solve your problem.

%dummy data
a=rand(1024);
b=rand(1024);
%create shorthand arrays with logical indexing
a1=a(a>b);
a2=a(a<=b);
b1=a(a>b);
b2=a(a<=b);
ab = (a1-b1)./(a1+(2*b1));
abavg = mean(ab(:), 'omitnan');
abSD= std2(ab);
ba = (b2-a2)./(b2+(2*a2));
baavg = mean(ba(:), 'omitnan');
baSD= std2(ba);

MATLAB: Elemental matrix multiplication [NxN] and [1xn] into [NxNxn]

a=rand(4,3)
b=rand(1,6)
[n,m]=size(a)
p=numel(b);
c=reshape(bsxfun(@times, repmat(a(:)',numel(b),1),b')',n,m,p)

Best Answer

Related Solutions

MATLAB: If else statement for elemental comparison

MATLAB: Elemental matrix multiplication [NxN] and [1xn] into [NxNxn]

Related Question