How to index two vectors according to some condition

Hello friends, Let’s say I have two vectors with the same length

x=[ 1 -3 0 -7 5 7 0]

y=[ 9 -4 8 -9 4 1 8].

I want to find out the index (with respect to the two vectors) where both vectors (simultaneously) have closest negative value to zero. In this case, the index will be indx=2 (x=-3 && y=-4). In case if there is no negative values in both vectors like

x=[ 1 -8 0 8 -5 7 0]

y=[ 9 5 0 0 0 1 8]

I want to find where x has largest negative value and y has zero value. In this case indx=5 (x=-5 && y=0)

Hope this question is clear and I’ll appreciate your help.

[Paolo]

In the first example, should the index not be 4 rather than 2? Since you have -7 in x and -9 in y.

Your second example is also confusing. Why would the index not be 2? You have -8 for x and -4 for y, both the largest negative element in the vectors. Could you please clarify?

What should the output be for:

 x = [ 1 0 2 -2]
 y = [ 1 -3 3 2]

?

[Hamza Makhamreh]

Thanks for your comment Paolo.

I corrected the question to make it clearer. I want the closest negative values to zero (I said largest negative value).

The case you mentioned is not occurring in my problem, that's why iam not considering it.

regards

[Stephen23]

"I said largest negative value"

Generally in English the "largest negative value" would be considered to mean the negative value with the largest magnitude, which is how both Paolo and I understood it.

[Hamza Makhamreh]

Yeah I see. Anyways, thanks guys...

Answer 1

[the cyclist]

I think this does what you want

% Case 1
x=[ 1 -3 0 -7 5 7 0];
y=[ 9 -4 8 -9 4 1 8];

% % Case 2
% x=[ 1 -8 0 8 -5 7 0];
% y=[ 9  5 0 0  0 1 8];

pairDistance = abs(x+y);

bothNegative = (x<0) & (y<0);
xNegAndYZero = (x<0) & (y==0);

if any(bothNegative)
    [~,idx] = min(pairDistance./bothNegative);
else
    [~,idx] = min(pairDistance./xNegAndYZero);
end

[Hamza Makhamreh]

Thank you sir. I expected that you are the one who will answer this question. Thanks...